Pros
ADP has fantastic training and is an excellent stepping stone for your sales career. After 2 - 3 years of experience and at least 1 President's Club you can almost write your ticket to any number of higher level sales positions. Income can be good, but is dependent upon your territory (see cons). Benefits and things such as Stock Purchase program are solid.
Cons
Be very cautious of your market. Your success greatly hinges on your market and your specific territory. While ADP is trying to ease this with the ability to network outside of your assigned territory, you are still dependent on your specific accounts or zip codes. Unfortunately, at ADP it's not necessarily 'the man' but more so 'the land' that determines your success. Client roles and Up Market roles are most likely to succeed on a regular basis. Advancement is possible but again, depends on your market/region and territory.