Mooneys are awesome airplanes... But do you know which Mooneys you're interested in? Generally, there are the short-body ones (M20C being the most popular), the medium-body ones (M20F and M20J are very popular), and the newer long-body ones. I've never even ridden in a short-body Mooney, but I've heard the back seats aren't really suitable for adults. I've flown an M20J and we had an adult in the back seat for an hour or hour and a half and he didn't complain... But he was also a big aviation enthusiast. The long-body Mooneys are quite roomy.
I'm the caretaker of a 1996 Ovation (M20R). The numbers everyone asks about: I get about 170 KTAS on 12 gph running at 64% power.
Generally, a flight in the Ovation goes like this: Everything firewalled for takeoff, fuel burn is at 25 gph. Gently pull back at 64 KIAS and it'll fly off at about 70. You'll quickly accelerate to an initial climb speed of 85 KIAS. Retract the gear and flaps, Vy is 105 KIAS. Above about 1000' AGL, accelerate to a cruise climb of 120 KIAS and you'll still be climbing 1000 fpm. Fuel burn in the climb will be down to 18gph or so by 8,000 feet. I run WOT and 2200 RPM leaned to about 25-50º LOP up there for the aforementioned 64% power at 12gph and 170 KTAS.
Getting this slick bird down on the ground is fun, too... A 500 fpm descent and 180 knots is about what I'll usually get, meaning about 6nm per 1000 feet of descent. I do actually calculate it based on headwind/tailwind component and usually add a bit of a cushion to allow for slowing down as well. So, on a normal day where I'm cruising at 8000 feet and field elevations are close to 1000, I'll start the descent around 45nm from the destination. I'll pull the throttle just slightly as I descend to maintain cruise power of about 23" MP. About 15-20 miles out, I'll pull it back to 20", 10-15 miles out back to 17", and 5-7 miles out back to 14" which is about as far as I can go without setting off the gear warning. Initially, I'll be at 160 KIAS in the descent, and by the time I'm at 14" MP I'll be at 145-150 KIAS. Vle/Vloe is 140 KIAS. If the 6nm/1000 feet descent gradient holds true, I should arrive at pattern altitude and make the power reduction to 14" at about the same time, and leveling off at TPA helps the plane begin to slow down more. I drop the gear at 135-140 KIAS, which quickly helps me slow down to Vfe (110 KIAS), and that's about where I'll be as I prepare to enter the pattern, at which point I'll also pull the power to 2000 RPM and push the prop and mixture forward. Initiating the descent from pattern altitude, I'll add the first notch of flaps (which pitches a Mooney DOWN, unlike most other airplanes) and pull the throttle back to 1500 RPM. Final notch of flaps on base, turn final. The final approach should be stabilized at 75 KIAS for a normal landing. Pull the power out, flare, touch down, pop the speed brakes out and hold the nose off and just let 'er roll. I try to use as little braking as possible - In many cases I'm landing the Mooney within a couple hundred pounds of its 3200-pound max landing weight, which is heavier than the 182 at max gross. So, I try to brake gently if needed - If I land on 15L at the home drome (4100' and just slightly uphill), I can use no brakes at all on the rollout, but I do use the whole runway to do that. With brakes, it's quite easy to land on half that if you want.
Full fuel payload is 495 pounds, but - With 89 gallons usable, I can take off, climb to altitude, fly for 6 more hours after that, and land with an hour reserve in the tanks. Because I rarely want to fly for that kind of time/distance and because the fuel at the home 'drome is expensive, I rarely start out with full fuel. For a trip with other people, a climb+3hr cruise+1hr reserve fuel load leaves me with 711 lbs of payload and about 530nm range. I've also done in-state flying with 4 good-sized adults. So, there's a lot of flexibility in terms of trading fuel for payload.
Pros: If you're tall, there's no plane more comfortable than a Mooney. They're insanely efficient at pretty fast speeds, which is great in these days of high fuel prices. They're pretty sporty to fly (Full aileron deflection is only 45º from center on the yoke). I really like the Mooney!
Cons: You'll have to constantly listen to other people repeat old wives' tales about how Mooneys are small and cramped inside (FWIW, I fit *much* better in a Mooney than I do in a Bonanza), how you can't land them on grass (you can), and quite a few others, none of which are true but people who have never flown a Mooney at all will swear that they are true!
Where are you located? There may be someone here who's willing to give you a ride in their Mooney if you're nearby...
And, for what it's worth, the one I'm flying right now is for sale. It belonged to my uncle, who passed away in February. He took excellent care of it, and I couldn't let such a nice plane rot away in a hangar, so I'm flying it, keeping it well-maintained, and working on selling it. I will be sad to see it go, though... It's a really nice bird!