The interviews are designed to be challenging - you're going to be asked to drill deep in a particular area or change course (depending on whether you have already covered enough ground or if it looks like you're stuck). Definitely look at Glassdoor for representative questions and practice ahead of time. I enjoyed this process. The Product sense and product execution interviewers let me know they would be taking notes and would interrupt me from time to time. That made it easy to take it in my stride.
It took them over a week to let me know of the outcome since their debrief meetings kept getting postponed. The recruiter kept me informed throughout the process so I was aware of what was going on.
My sense of the culture from the interviews was, they definitely look for a certain type of attributes in the types of PMs they hire - think fast on your feet, highly articulate and succinct. They certainly screen heavily for those attributes/characteristics. If you can nail that during your interviews, you will do well.