Pros
Fast is a great company to work for. They have a great salary scale and raises come often. The benefits really can't be beat, they believe in treating us as well as possible. It really is a company based around work hard, play hard as well, the company likes to party (in general, there are people who don't and thats fine too).
Cons
This is no stepping stone job. You will learn and grow professionally, but much of the programming knowledge you will gain is not applicable anywhere else. You have to be willing to move around and know that you don't have much choice in where you go. This can put strains on relationships and be a little stressful at times, but you are always moving to a new site that is full of people in the same situation, so there is almost always a good fast community. It is also a fairly flat company, with really only 2-3 feasible levels you can get to, base programmer, team lead, and project manager/architect. Raises come with new positions, but they also come regularly without changing positions. There are people in the company that have a lot of years under their belt while staying at the base programmer level.