Pros
You get to help people with problems. You get to do what you're good at. Usually cool co-workers. Most of the techs are really highly competent despite the universal notion that anybody who works at GC can only be a buffoon.
Cons
1. Repair techs are in SALES as much as any commissioned sales floor guy. The fade system for techs--you are required to be 'cost neutral' by charging enough per month to cover your hourly pay. If you don't have enough customers coming in or the repairs they need are not expensive enough to hit those numbers, you have a big employment problem. In order to make this amount, you are required to continually be 'upselling' repairs and upgrades that the customer may not need or want. 2. The hands-on training is terrible and absolutely insufficient. A two day seminar at a hotel is the extent of training for fretwork, bracing, cracks, reglue, etc. The rest is by 1-3 page PDF documents. I was sent a powerful and dangerous router and, with no training whatsoever, told to rout holes in a board and send in pictures. I did and now I'm 'A Level Certified' to go to town on your Les Paul. If you contact one of the three program managers with a question, your likely response from two of them will be "Really?" punctuated with a sigh. The third will basically chew you out for calling him instead of one of the others. Finally, point 3. The embarrassment of telling other local and respected techs and luthiers that you do the same thing as them, but at Guitar Center -- it's like telling jet mechanics that you pump gas at Wal-Mart, no matter how good you may actually be. Not a good thing should you try to find local employment in the instrument repair field after after GC dismisses you, which they will.