I wouldn't describe the interview process as difficult, more like time consuming and wasteful. I worked very hard to prepare myself, I took time off from my current job to be able to meet their long interview hours (I spent grand total of 5 hours interviewing with this company, only to receive a generic rejection letter from a recruiter that I had never spoken to. The letter had spelling errors and a blank space where the name of the position I applied for should have been which really indicates to me how little they cared about the process. This was very much a waste of time and I can't imagine that they did not know they were not interested after the first four interviews which were an hour long each which leads to a feeling of being lead on. I am very disappointed by the amount of work I put into trying to be a part of this company to be handled in such a way.

3 rounds: hr, peer, and mgr. The overall process was smooth. The recruiter was really responsive and helpful. The only down side was the leader took weeks to make a final decision probly because he was interviewing many candidates in the meantime.