Based on my experience working on different teams and interfacing with the SA teams (but not actually working as an SA, mind you), being an SA at AWS seems to be one of the better positions in terms of workload, limited on-call responsibilities, etc, but you do need to be very comfortable with constant customer-facing responsibilities (which can sometimes be better than on-call, and sometimes can be worse than on-call) and the team is still dragged down by the general Amazon/AWS culture.