I had 5 separate interview sessions with 2 individuals at a time. Each group was allocated 15 minutes to ask me questions. I only had one technical test (the second round) where I was asked to use any programming language to sort numbers. That was easy since I'd been doing programming exercises everyday (highly recommend this for at least a month before interviews). Talk through your approach during the technical test (they want to see how you think). I interviewed with people older and younger than me. (I'm in my 30s) After each interview session, I was taken to another office.
Overall the experience was lighthearted and enjoyable. I didn't feel too stressed because it seems like my ideal work environment: nice people, own office, time to think, not too fast paced, fun projects, etc.
The only thing is that I've been waiting over a month (interviewed in mid-June 2015 and we're now in late July) to find out if I got the job. Today I finally get the call and I miss it because I'm in the shower lol. I'll update as soon as I find out if I got it.