I'm actually a crossfit coach at an affiliate. I started out as a client, but got my L1 certification over a year ago and have enjoyed the $300 change in my monthly cash flow that comes from teaching 3 classes a week. There's lots of info (and mis-info) in this thread, I'll try to take on a little.
Affiliates are expensive. Typically $100-150 a month. There are lots of explanations for this online, basically it tends to weed out people who are not passionate, and makes for less work that the coaches have to do. I would rather coach 10 people each paying $100 than 100 people paying $10.
Depends on the gym. I've met certified crossfit trainers who shouldn't be allowed to take care of a houseplant. I've met others who are passionate, intelligent, and work hard to be the best coach and teacher they can be. In my experience, more fall into the latter category. I try to fall there myself. I spend hours each week doing research, reading about technique, and watching videos of other coaches I admire to learn from them. Unfortunately, anyone who can pay $1000 and take a really simple test can become a L1 Certified instructor, so you do get meatheads who emphasize intensity over technique. If they had paid attention at their $1000 certification class, they would know better. We have some people come in who have been doing it on their own (off the mainsite...see below) who have bad technique that sometimes borders on downright dangerous. They may be strong and have excellent work capacity, but almost universally their technique and output can be improved significantly with a bit of coaching.
The crossfit.com main site posts a workout of the day (WOD) every day. The recommended weights/moves/rep schemes are intended to challenge the most elite athletes in the world. Some of the people who contribute to the programming are Olympic athletes, Olympic coaches, Professional MMA fighters and coaches, Exercise scientists with PhD's, and many other very smart people. Some of the lifts (snatch, c+j) are very challenging and do require quite a bit of instruction.
The best part of working out and working at an affiliate is the community. We have sports competitions (volleyball tournaments, football tournaments), bbq's, and tons of other fun stuff because it's a large group of energetic fit people.
The competition aspect of crossfit I feel is a big negative. It encourages poor form, injuries, unregulated supplements, and a lot of hurt feelings. A big part of the original crossfit method was that it was something you could do your whole life, and would keep you healthy with an emphasis on overall wellness rather than absolute performance. Now the emphasis seems to be on pushing yourself past the limits in order to be a better exerciser than anyone else. There are a few people in that category at my gym, but the majority fall into the category of "I just want to look good in a swimsuit and have fun after work instead of watching TV."
Sorry for the huge wall of text, but as you can see I'm a cult member and feel very strongly about all this. I believe in theory that the randomized crossfit method is incredibly effective in theory, but in practice sometimes gets bastardized into something that makes the community at large look bad.