Fairly long and drawn out, even relative to other positions at Google:
1.) Recruiter contact/interest screen
2.) Technical phone screen focused on problem solving and general technical ability
3.) Technical phone screen focused on coding and design
4.) Four-plus hour (with lunch) on-site interview round covering design/architecture/problem solving, sales and client facing skills, and coding
5.) Group presentation followed by a Q&A panel session (at the end of the onsite round)
Coding questions are somewhat more difficult than average, but still nowhere near as challenging as those you'd typically get in a software engineering interview at a very selective company. That said, given the number of hats you're expected to wear in this role, questions will cover a wide breadth of topics which makes the overall difficulty of the interview fairly high.