A phone screen with an HR rep, then two separate Skype interviews (due to availability of interviewers). There was an on-site interview with a panel of 5-6 people and a follow up phone call with a Senior manager as well. Overall, the process was simple and reasonably fast.
If you're expecting plans to be firm and aren't open to last minute changes, you may have a bad time. I never got the feeling that it was a lack of respect for my time, rather that it's the typical chaos of a start-up.
The panel I got to speak with during the on-site was really great; it was laid back and I got to ask questions that gave me a good picture of what it's like to work there.