Pros
I went through the courses at Code Fellows as a student and loved it. After graduating, I became a teaching assistant so that I could make some money while searching for jobs. That was a great opportunity to take the classes again for free and to solidify my understanding of the material.
Working as a TA also game me time to solidify my understanding of the material. I essentially got to take some of the classes again for free, and I found that teaching code constantly was great practice for whiteboarding. Also, teaching there is a great way to develop your network, build up rapport with the faculty, and get job experience in a programming job.
Cons
Code Fellows is a code bootcamp, so it produces a constant stream of people looking to get work. Since they normally hire TAs from among their graduates, the applicant pool is huge, and because they often don't know full enrollment numbers until close to the date that the classes start, it is hard to secure regular work as a TA.
The coursework at Code Fellows is constantly changing as they refine their curriculum and stay up-to-date with emerging trends in tech. As a result, even if you're teaching a class that you took recently, the work that the students are doing may be quite different from what you did.
Also, since teachers usually need to prepare the next day's lesson or attend meetings, the brunt of answering student questions falls to teaching assistants. Even with so many teaching staff per student, being a teaching assistant can be exhausting.