I bought a membership with their big client. The first 2.5 shops covered the purchase, and as another forum member reminded me, I can claim the cost of the membership as an expense on my taxes.
The shops are very easy and quick--they don't want you wasting the agent's time. There is a 6 month rotation, so I'm sitting out now. In my area, the job board only shows shops for that one client. "Travel" bonuses are often added.
QAMS is easy to work with. They pay by check about 2 weeks after the shop. If there are some in your area, go for it!