Two technical interview over the phone, about an hour each. One in-person interview, consisting of approximately 5 hours of back-to-back technical interviews and concluding with a conversation with HR. I didn't hear from them for a month, then they made an offer over the phone. They fell out of touch after making the offer over the phone for approximately a month, and then informed me that they were rescinding their offer. They did not provide a reason. They seem poorly organized and minimally concerned with the fallout from their miserably dysfunctional recruitment process.

Recruiter phone screen, technical phone interview, on-site technical interview, meeting with upper level manager. The whole process took a very long time, and I actually ended up finding, interviewing and accepting another job offer before the final interview stage. Most of the people were very pleasant and extremely intelligent - they ask difficult questions, but it was okay to admit not knowing!