Work life balance is non-existent, and you'll be expected to be "on call" 24/7 (despite this, there's no reimbursement for cell phone plans...or parking for that matter).
Attrition, despite what their official responses say, is very much a problem (even a director confided to me that it was really bad and no where near average rates for other consulting firms). I saw people last about a month before they found something better and moved on. Can't say I blame them.
They choose to keep a workplace bully just because he brings in a lot of money and at some point or another, he WILL butt heads with you in the most unprofessional way. Be prepared that if he schedules a meeting with you (actually, this goes for just about any manager), he'll stand you up numerous times until they finally meet with you 20-30 minutes late). Despite being hugely unprofessional and sometimes down right out of line, he's still there and one of the head honchos. Talk about hostile work environment. He talks a good game and can be very motivational in all-hands meetings, and then none of that really plays out.
The employees aren't the priority - I mean, heck, they refer to us simply as "resources" - the client is very much the priority. Managers are partly project managers but mostly salesmen and it shows. Don't expect them to have a good grasp of your daily project work since they just don't have that background.
Be prepared to drink, so if you're a recovering alcoholic keep that in mind.
Hope you want to work for Microsoft, because you'll end up there eventually. They're always trying to attract new clients and having success with that, but the majority of projects are at Microsoft and very similar to staff aug.
You'll have no say whatsoever in the types of projects you're put on and no heads up on what they're considering you for. While on the bench, I would be told around 11 am that I had a phone interview at noon (so no real time to prep).
The benefits ranged from so-so to nada but they were working on improvements. Salary, however, really was disparate. Being paid $20K less than industry average happened often and annual raises, even with a great review, was tiny. The yearly bonus was usually nice but certainly didn't make up for the hours of overtime you worked.
Speaking of which, be prepared to be put on multiple projects that add up to more than 40+ hours a week. They're essentially charging the customer as if he's getting a dedicated consultant at least part time, but the same person could have a full time project as well. So yeah, they're making money off of you but certainly not coming close to trickling any of that down to you.
Reviews are a laborious process twice a year and follow the Microsoft model to a large extent (I never really got the feeling of a stack ranking persay, but the culture of it all felt a lot like it).