Very thorough process - about 7 interviews spanning 4 months. I first worked with an internal recruiter on initial screening before she helped coordinate the team specific interviews. Not being near HQ (SF) most interviews were over the phone. For the final interview I was flown to SF to meet managers and conduct a mock client presentation.
In addition to skills, there was great emphasis put on personality and culture fit. Read the glassdoors reviews. The employees are generally smart, positive, driven and a tad quirky. The entire process was a little arduous, but if you are confident, friendly, and know what you are talking about then you should be in good shape. I found it beneficial to take an active role in the interview process. They're growing, keep following up.
Definitely do a lot of research on the company, the product, and their customer service philosophy. They strive to be thought leaders in the space and want to know that you'll join on that mission. The website is packed with useful content. The book 'The Effortless Experience' is a big influencer on product and philosophy. If you want to know more about the history of the company (and you should!) read the CEO's book Startupland.