I worked at Amazon through this company in 2010 in peak season. There was almost no communication the entire time I was there. They changed the time that paychecks were picked up without telling anyone, after I (and about thirty othe people) had stood for an hour outside the buliding. That was after I finally figured out where to even pick the thing up. Nobody there seemed to know the answer to anything. I wouldn't go through them again.
The folks at Integrity were very helpful. I started as a seasonal worker and have just recently been hired by Amazon. during their busy season, Integrity does have to interview thousands of people and this can take some time, but hey, there aren't many jobs out there. Who wouldn't wait. Integrity got me started on what I hope will be a long term job at a cool company.