They hire the best of the best. They only want professionals to represent them at their client's place of work. When you work for ASAP's clients, be prepared to shine.
Cons
If you don't like being a consultant for another company, then this may not be the place for you.
There is a strong professional support system that guarantees your success at the client site. You are always trained, if you are new you are assigned to a mentor; if you are a seasoned professional with some tenure, you become a mentor. This is a true team spirit, where the success of all is based on each individual success.
Cons
Lots of red tapes, they are flexible to some degree; but if you are planning to take a long vacation (1 month), you are expected to return all your equipment and badge. You may or may not be able to return to the client site.