Pros
Good pay, good benefits, and a whip-smart team that is extremely capable. Catered lunches and a stocked kitchen go a long way toward making sure employees are satisfied in their day-to-day. Work-life balance is great until times get tough, then it's time to buckle down. But, hey, you wanted to work for a startup, didn't you?
Cons
If you're not a go-getter and up for actively pursuing professional development, it's possible that you'll stagnate.