There was a phone interview with two very weak, very easy technical questions (e.g. basics of binary search). I then went in for a day with two 45-minute interviews, followed by a day with 3 interviews. Due to scheduling constraints, they scheduled next-day interviews (!), but as a result, one of the interviewers didn't show and I had to go find the recruiter, who found me someone else after a bit of apology and hassle.
The interviews tended to be very similar. First, I'd be asked to talk about some sort of interesting research I did. After that, I'd have one or more algorithm/coding questions, where the first part would be to explain the solution to some algorithmic problem, and the second part would be to code it up. Sometimes one of the parts would be omitted, but every interviewer wanted to see code on the whiteboard.
I liked the open feel of the office and culture, but found that people seemed more driven by the company's success and profit than by the fun problems they got to work on, which left me a little less attracted. However, for someone with more interest in business success than I have, that might be ideal. I'm sure there are interesting problems there, and there are plenty of smart people and it's a flexible environment. The vacation time is among the best, though other benefits are still lacking (e.g. investment matching). Compensation included a large proportion of stock grants, the value of which is still uncertain.
Due to my timidity, I did not engage in any compensation negotiation, and my recruiter did not bring up the possibility of increasing it, which surprised me given that they knew I had a competing offer. I found that somewhat unwelcoming, but perhaps it's standard.
