HighFlying380, you've asked a question that will definitely spur people towards their keyboards! In the end, though, you'll have to decide for yourself.
One thing I don't think has been mentioned is that all your costs are tax-deductible. That includes mileage driving to meetings.
As you can probably conclude from the various responses, the situation varies from squadron to squadron and from state to state. So if you decide to go ahead, visit all of the squadrons that are within your acceptable driving range.
As several have said, the free flying is not all that common. Training weekends, called SAREXs, might get you two to five hours a few times a year depending on other pilots' wanting to fly also. Ferrying airplanes between squadrons and maintenance is free flying but in our state at least this tends to be done by an old boys' club largely made up of usually-available retired guys. They're not really trying to freeze others out, it's just that when a ferry is needed the old boys' club is in the ops guy's cell phone and he knows he won't have to make more than a couple of calls. The alternative, notifying all the pilots in the state of the opportunity, just makes the ops guys' lives more complex without providing them with any benefit.
As has been said, the paperwork and BS is unbelievable. Every petty bureaucrat from the local squadron to the national commander has his requirements and has placed hoops for you to jump through. None of them care about how much of your time, collectively, this takes. It takes a lot.
But --- it's the only place I know of where I can fly a half-million dollar airplane for $20-50/hour (depending on the state) plus fuel. If you're trying to build time, this (tax-deductible, remember) cost is the lowest you'll find. There are G1000 182s and IIRC 206s in mountainous states. Also lots of (cheaper) 172s, including newer refurbs arriving with G600 panels. There are also a few Gippsland GA-8s, which are interesting to check out in but boring and uncomfortable to actually fly for very long.
Actual missions are infrequent. I have been on three in the last twelve months, probably a personal best. One, or maybe none, is more typical. If you are constrained by having a job, heavy mission participation is difficult. One of the missions, again unusual, ran for over two weeks.
So -- join for the opportunity to build cheap, tax-deductible time. Don't join if you can't stomach petty bureaucrats and paperwork.
Another waste of tax payer dollars.
Complete nonsense. The Air Force has the domestic inland SAR mission. Last week a friend and I spent 1.9 hours of 182 time chasing down a crashed 206 amphib. (No injuries, it was hidden in a hangar -- the guy didn't want to tell the NTSB/FAA about it but he forgot about the ELT. ) Had the AF not had CAP, this job would have been done by a Guard Blackhawk or a Guard C130. At what cost? I dunno. A hundred times more? A bunch of little airplanes, flown for free by guys is blue polo shirts that they've bought for themselves, is clearly the cost-effective way to go.
(That's not to say that CAP couldn't be more cost-effective by, for example, focusing ONLY on the SAR mission. It could. But there's not a chance in Hades that the military could do the inland SAR mission at anywhere near even its current cost to maintain CAP.)