Efficient. Phone screen by recruiter and hiring manager followed by day-long on-site. All the usual questions, as you would imagine for such a role, and everyone professional. Focus on people mgmt and agile dev process. The only interview that was a real chore was with one of their agile PMs, who was quite robotic, and mainly wanted to discuss his own achievements.
Lunch is provided, but it was with the whole company at their daily catered lunch, so a bit of a chore to sit down and make small talk with 10+ people you have never met before. However, I think this is a sociability test, but still a little awkward/inappropriate I felt, especially in middle of marathon interview session. We subsequently did dinner one evening with the smaller team with the open req and CTO, and that was great. This is a much better test of team-fit, I feel.
Ultimately, when it came to the offer, we could not agree on renumeration, as they came in a little low compared to current salary. Also, the stock option grant was derisory, which might have been a nice off-set against lower salary, but alas it was next-to-nothing.
All in all, though, a great team and super product. I was very close to saying yes.