The interview process began with a phone interview to determine fit, followed by a very long in-person fit and technical test.
After a brief phone interview, mostly to verify my resume, to talk about the company, and ensure I wasn't a complete sociopath, I was invited to interview in person. The transition between the two took awhile, as it was the holiday season, but I ended up interviewing within 3 weeks, and getting an offer within a week of that.
The in-person interview started with a half-hour interview with various people to gauge cultural fit, and as an opportunity for me to ask questions and get familiar with the company. The second portion, which was approximately an hour long, was the technical test. I really enjoyed this process; I was given two developers from their team to work with, and together we group coded an activity to see how I work with the team, and if I had the technical skills to deliver on the product. It was a really great exercise for me to see if I felt comfortable working within the context of the daily routine. It also gave me a really great feel for the people themselves.
All in all, it was a really positive interview process, and I ended up taking a position with them.