As most people have experienced in interviews, you really have no idea what is expected of you, for example "surprise! take 2 hours to write a complex SQL script on the spot!" or what you're going to be asked.
After interviews with many companies and having been in a previous role interviewing, I found the CircleBlack process very refreshing.
There were three concise interviews: One with the technical recruiter, one with the direct manager for my position, and one with the CTO.
Each lasted 30 minutes to an hour. They were very conversational and comfortable.
The process for myself was very quick and communicative. None of the "well, we interviewed you a few times for a total of 6 hours and we'll let you know in a few weeks" deal. I've found if an employer has to spend that much time interviewing and cannot decide on a hire, they are asking the wrong questions.