The interview process started out great for me but quickly detoriated. Originally, I applied for the software engineer position, and after the regular phone screen + code exercise, I was asked to come onsite (took a full day - 7 hours or so). The onsite was very difficult - a lot of algorithm-heavy problems to solve: expect graphing problems, recursion problems, map-reduce problems, etc.
After the onsite, the recruiter let me know that I didn't make the cut for the software engineer position, but they liked me for the Scrum Lead position. She told me that I wouldn't have to go through the entire loop again (and definitely not another onsite) and probably just another few phone screens. A few days later, I talked with the VP of Engineering, and he said I had to go through the entire onsite loop again. At this point, I still liked the actual company and what they were trying to do and their culture a lot, so I did the second loop. I was specifically told that this would be the last step and I'd know a decision by the end of the second onsite.
The second onsite went relatively well (or so I thought), and then the recruiter got back to me saying that I had to do another *two* phone screens afterwards just to "make sure" that I was still a good fit. At this point, I had to decline the next step, since I was already running out of time on my other (really good) offers.
Bottom Line: After 5 rounds of interviews, they still could not make a decision on whether or not I was a good fit for a position that *they* reached out to me about the second position. Another concerning point was that the Scrum Lead position had different roles and responsibilities depending who I talked to and when I talked to them, so it seems that they haven't fully figured out the position themselves. Quantcast has some great products and ideas being engineered and a really nice culture, but they definitely have some issues to work out in terms of the recruiting process and decision making.