I went through many interviews with Rocket Fuel. I did one 8 hour take-home project, probably about 5 phone interviews and the whole day on-site. It didn't seem like the recruiter was going to call me back either, but thankfully I followed up with him. They didn't give me any real feedback as why I wasn't getting the position, so that was disappointing.
That being said, I thought the interviewers were very pleasant to meet and talk to. If I had to give feedback to Rocket Fuel, I'd say that they need to streamline their interview process (several unexpected interviews happened in my case). Also, more feedback should be given to the interviewee, especially after such a long process.