How many have noticed a lot of other pilots skipping it?
I don't usually pay close attention to what others are doing, but sometimes it's very noticeable.
We had a flight engineer who was infamous for doing his walk-around in the crew van while approaching the aircraft. He got snagged by a European SAFA inspection, which is like an FAA ramp inspection. The SAFA folks often sit in a vehicle at a distance and watch, before ever approaching the aircraft to inspect, and if one hasn't done a thorough preflight, carried a flashlight, worn the ubiquitous orange safety vest, or clearly inspected the aircraft, they've already got marks against you. In fact, they've already done a preliminary inspection before we ever show up, and have items that they'll ask about that they've already identified. They don't miss much.
I've seen the FAA do the same thing. I've also participated in FAA contests involving a preflight in which they've altered certain things on the aircraft. The winner finds the most discrepancies. I won a Snap-On screwdriver from the FAA that way; I identified 12 more discrepancies than they created; it was 12 more than they found.
I look for more than is in the aircraft flight manual. If I'm looking at safety wire, I'm checking to see that it's wired correctly (surprising how often it isn't). I'm looking at self-locking nuts to see that at least one thread protrudes past the nut, and that castelated nuts are properly secured. I check everything I can see, or touch or move. I check fuel by smell, sight, and feel. I check it at the sumps and dip my fingers in the filler neck in the tank. In the case of avgas, if it's slippery and dries white, it's probably right; if it's slippery and dries oily or clear or not at all, it's probably not, and if it's not slippery at all and doesn't dry so fast, it's probably water. I've found differences between what's in the sump at at the filler neck. I look in the tank for debris. I rock the wings, raise and lower the empennage, move water and shake it free from around baffles. I shake wings and check for noises and move and tug on everything I can on the airplane.
I've found tools in place, controls rigged backward, missing panels, missing safety wire, safety wire looped around propeller governors (disabling them), hydraulic leaks, fuel leaks, broken parts, spools of safety wire where they shouldn't be, and all sorts of other things, from illegal repairs to inoperative components, to missing control surfaces.
I once preflighted an airplane the day before it was needed for a search. Early the next morning we were called for the search, and on arrival at the hangar, found that the elevators were missing. Someone had moved it out of the hanger the previous night and parked a vehicle in the hangar. They backed it into the vehicle in the dark, trying to move the aircraft alone, and then they removed the elevators to have them repaired (the person who did it was a mechanic and inspector). No note, no explanation; we showed up to an airplane that I'd preflighted before putting it in the hangar, to find the control surfaces missing.
Never assume that because you preflighted it last night, it's in the same condition this morning.
If I am interrupted during a preflight, I start over. I don't try to pick up where I left off. I made that mistake during a pack job on a parachute once, and ended up in intensive care; if you have to stop your preflight or inspection to attend to other matters, for any reason, then start over. It's a small price to pay to ensure everything is covered. The same with a checklist in the cockpit. Unless it's a point in the checklist that has a hold built into the checklist, run that checklist over again. It's simple, doesn't take much time, and ensures that you've covered everything on the checklist.
You may think that if you fly a hundred hours a year, or are in your own airplane that you know so well, then that's overkill; it doesn't apply to you. It only applies after all, to professionals flying the same airplanes eight hundred hours a year, who do it for a living, and who have a lifetime of experience behind them.
I always post-flight. If your post flight inspection isn't as thorough as your preflight inspection, you're doing it wrong.
When I land and fill the tanks, I watch what goes into each tank very carefully, and match it to my calculations, the fuel flow readings, and the measurements taken during the flight. How accurate was each? I find out when we put the fuel in the airplane, and I take that into account. I do cool-down runs on the engine before shutdown, and post flight run ups, mag checks, and idle mixture checks in piston airplanes. I idle turbines for five minutes after the final power reduction, before shut down. Same for turbocharged airplanes; five minutes minimum after last operating the engine below barometric pressure.
One shouldn't neglect shutdown checklists or procedures. The tendency is to shut it down, tie down, and walk-away. If a checklist is useful for the before start or before takeoff phases, it's equally useful at the shutdown and parking phases. Use it. The post-flight walk-around and inspection should be just as thorough as the preflight.
As a normal part of the preflight in the cockpit, I move or touch or test everything I can in the cockpit. If there's a test or inspection associated with any particular item, I do that, form press-to-test lights to VOR checks, to systems checks, to radio checks. Everything gets tested and checked. Paperwork gets examined. Flight plans get checked waypoint by waypoint; I check latitude/longitude, distance and bearing between each, total distance of the trip on paper vs. what's in the box (whatever box may be in use), all the fuel calculations against what I've got, agains the latest weather and desired extra reserves, and so forth. Generally one hour minimum in the cockpit getting ready domestically, and two for anything internationally.
During fire season I start early; I began several hours before the start of duty today, which is typical. I'll typically continue several hours after being released, depending on the length of the duty day and what's planned for tomorrow, taking into account the need for rest between duty and flights.
With a student involved, I try to plan on a minimum of an hour before any flight for the student and the preflight; longer if material needs to be covered by way of briefing or training prior to the actual flight lesson. Always at least an hour after, or more. When training at work, typically two hours for the pre brief, then one to two hours after each training session for the debrief. With students, I like to move switches, hide things, and mix things up a bit to give the student "easter eggs" for which to hunt, to see how thorough their preflight may be. Hopefully they'll find the tennis shoe on top of the engine cylinders, the car keys by the fuel selector, the rubber snake out of sight around the nose gear linkage, and so forth.
Constant speed propellers should be checked for security, but also each blade should be checked for leakage around the blade seal, for play in the blade (fore and aft, and by way of rotation). The engine controls should move freely through their full range, as should other controls (tailwheel locks, flap handles, etc). Check everything. In a small airplane, I run my hands over the skin, touching everything, checking for things I might not see, but can feel.
In tankers, washing the airplane has always been part of my regular inspection: a great deal of attention gets paid to the airplane when it's being washed (and waxed); a single smoking rivet, a crack, or other things that develop, are more easily seen when one is in close contact with the airplane for extended periods every day. Some years ago, two airplanes that I used to fly lost their wings in flight, killing all the crew members. In the case of the second airplane, I'd done my type rating in that specific serial number. I knew it very well. Every time I flew that airplane, it got thoroughly washed; a typical wash job took about 12 hours to complete, and if I wasn't flying, I always had a panel off, looking for oil leaks or any number of other things that needed attention. I spent a lot of time going over that airplane.
The pilot of the airplane when the wing came off was fairly new. He made the statement when he upgraded to captain that he wouldn't ever wash an airplane again. His copilot wouldn't wash an airplane at all. It's my opinion that had they been as thorough about the airplane, they'd have seen the problem that killed them, and they'd probably be alive today. I can't prove that, and it really doesn't matter today; they're all dead. Had they been more proactive and detailed in their inspections, instead of sitting in the air conditioned ready rooms waiting for fires, chatting and laughing with friends, I think they'd still be alive.
Airplanes talk to you. The only time you might hear them speak might be during that preflight inspection when the small crack, stain, droplet of oil or hydraulic fluid, or other hint is found. It might be your only warning of what's to come, be it a gear failure, engine failure, or other issue. The place to look for those things is on the ground when you have the luxury of time and the safety of zero altitude to do your preflight. Don't neglect it. It might be your last.
Always treat the preflight like your life depends upon it, because it does. Always treat it like it's your last time, because if you're not through enough, it just might be.
The lead is absorbed through the skin. Health effects can be quite sever and long term to babies. There is no minimum amount of lead exposure that is acceptable. 
