CAP
I was a CAP member for something like seven years. My experience was mostly positive. I gained flight time and experience and honed my skills. That was a major plus. Where I believe I derived a greater benefit was from the learning and personal development opportunities, and the fellowship.
CAP has the Senior Member Training Program which requires you to complete a number of personal development and leadership courses to progress in the organization. Many of the courses are written by the USAF at Maxwell AFB in Alabama, the home of CAP. These courses are similar, I'm sure, to the Air University courses that AF people must take to advance in their careers. People will scoff at these courses as being so much hooey, but they are not if you apply yourself. There is some real learning to be obtained.
The quality of fellowship depends on the unit. Larry is not wrong. Quite a few CAP squadrons are run that way - the aircraft become a personal empire for the guys he describes. But, in our squadron, we wanted the aircraft to be flown, and welcomed new pilots. Proficiency flying was not free and was heavily supervised, but the rental was far lower than FBOs. Our philosophy was the more the aircraft were flown the easier it was to keep them maintained. We also benefited from leadership that was devoted to running the unit professionally, and, for the most part, it was. We were friends with Wing Staff, which made a difference in accomplishing our goals. Moreover, many of our members were FAA people from the Mike Monroney Center in Oklahoma City. Yes, one was a fed, but he made a positive imprint on the flying program from which I personally benefited in terms of training.
I saw some of what Larry is talking about when I joined Arizona Wing. Our squadron was really an apathetic unit consisting primarily of retirees. It very much lacked the professionalism of my OKC unit. The wife of the Wing Commander was really the power behind the throne. The long and short of it was the organization was extremely political and was nothing like the CAP I knew.
The missions depend on their purpose. You might be called out in the middle of the night to fetch the ELT locator receiver and drive to the local airport to find it and shut it down. You might be called out on a SARCAP to locate a missing aircraft. You practice search techniques on a REDCAP mission. These are really a lot of fun. If you're a flight instructor, you might have periodic flight clinics in your wing, in which you give pilots annual Form 5 checkrides. In Oklahoma Wing, these were usually accompanied by a WINGS safety lecture put on by FAA personnel who were also members. I found that all this training was very valuable.
Bottom line is that CAP is a volunteer organization, which often are extremely political. I'd suggest you attend a meeting and see how you like it before deciding.
Hope this answers your question. Good luck with your experience.