It varies so much depending upon what squadron you get into that I don't feel comfortable giving you a real straight answer. I was in the CAP for several years, and at my squadron, there was a whole lot of BS to contend with. A lot of it came out of the fact that many of the members are engineers and office folks who get to be "Lieutenant Colonel Smith" one night a week. In a bad unit, it kind of becomes a twisted game of dress-up. On the other hand you can pick up some free and some cheap flight time, although I wouldn't call it a "time-building" opportunity. Expect to fill out lots of forms and stuff every time you fly. They have forms to confirm filling out forms. Lots of bureacracy and red tape. Go to a few meetings at the local squadron and try to feel out their attitude. If you don't like it, there may be another squadron nearby.
I was a CAP member for six years. Some of my fondest memories and best flight and personal experiences were from being in CAP. I got some early flight instructing experience in CAP, which was valuable, but the best experiences I had were from the fellowship and comaraderie, and the learning from the personal development and aviation-oriented courses and seminars. Note that I put aviation at the end, not because those experiences were of low quality; they most definitely were not, but because the personal development courses and training were so meaningful.
The quality of CAP experience will depend very heavily on your unit. I was extremely fortunate. Most of my CAP experience was in Oklahoma Wing. My unit was in Oklahoma City, and we had a great deal of contact with Wing staff. Our wing was run very professionally, and that greatly influenced my CAP experience. I got to know a few members of Wing staff. They mentored me and presented me with many opportunities to develop and hone my personal, organizational and leadership abilities. Our Wing flight standards officer was a real, live fed from the Monroney Center. His day job was to train DEs. He developed a course based on his DE course for wing and squadron check pilots. I took the course and helped put it on in my capacity as an Assistant Wing Check Pilot. That training stood me in good stead after I went to work at ERAU. I was promoted to Stage Check Pilot at Riddle. I had known for some time how to give a flight test per the FAA, so I was ready.
I saw the difference when I moved to Arizona. I joined the squadron near ERAU. The squadron was not run professionally at all. I went to one practice SAR and was disappointed with the lack of organization. I went to a wing conference and was similarly disappointed.
Once again, a lot depends on your unit. There may well be bickering, politics and agenda-promoting. You see these things in volunteer organizations. By the way, because CAP is a volunteer organization CFIs cannot charge for their services if performed in CAP airplanes. But, take it from me, in the right situation there are other rewards.
My unit was great. No bad experiences just alot of good guys doing volunteer work. Very often one of them would be up at 3:00 AM on a work night trying to track down an ELT signal -usually somebody forgetting to turn off the ELT prior to mailing it. UPS guys at the terminal hated us since they would have to unload the truck to find the ELT.
I remember one time the guys were out looking for an ELT signal in a suburban neighborhood in the wee hours of the night. Picture a bunch of folks with weird looking antenas in camouflage walking around your street at 2:00 AM. Naturally, very nervous police show up to find out whats going on. So one of the cops asks what they are up to and the response he gets from one of the funnier members is "we are looking for UFOs!". Dumb answer, but conducive to getting a gun aimed at you. I can tell you that was the last time he made a comment like that to the police and the police were always contacted first after that.
I remember CAP offering a ton of opportunities and great courses for free. Great for personal development. There was alot of paperwork and delays, forms in triplicate etc...but not unusual for government related organization. Most of the guys I met were in many civilian professions and alot of former military. The CO was a former Air Force B29 crew member from the Korean War. Very laid back, no I'm a colonel for the day stuff.
If you like aviation and want some volunteer work on your resume its a good way to go. In my unit, you could put in whatever time you were able to, there were no obligations.