Pros
Don't have to do too much when there are no customers around. Depends on the store location, but in my store, I simply sat around playing on my phone or watching movies on my tablet. The job is also a lot of fun. It's very engaging and it's always nice to keep up on new technology. If you're single, Prime offers special pricing on a new AT&T account. I basically pay $70 for a plan that costs $160. It's also a much better sales experience than typical retail.
Cons
People are pretty ignorant when it comes to cell phones and cell phone plans, so be prepared for a lot of dumb questions. Also, Primes a pretty cheap company. They rarely reimburse for travel expenses when you're sent to mandatory (and also not very helpful) trainings. There's very little training and there are some fairly shady practices for meeting certain metrics.