Phone interview with HR was routine, mostly general questions about your skills. They definitely ask, "Talk about a time you were met with a challenge during your job or a past project. How did you deal with it?"
They flew me to Kansas City to do the interview. I met with the HR person I talked to over the phone for about 15 minutes and she repeated some of the questions she asked over the phone, but she seemed kind of frazzled and was just reading off of a list. This time there were more personality questions like, "Rate in importance: salary, job, family, etc..."
After that I met with two managers--one from their technical team, another that oversees user interface design--and was throughly grilled by them or two hours. They give you a bottle of water. Throughout the interview they're typing away at their laptops and don't really give you anything except more questions. They ask detailed questions about your skills and experiences. Bring your portfolio.
After bring interviewed for almost 1 and a half hours, they present a skills test for you to perform in half an hour. It isn't anything too hard, just produce a pen and paper prototype of a user interface for, say, an interactive map at a mall and how would that look on a mobile device. I think they are looking for communication skill here and explaining why you chose this feature or how you would remediate a problem for such and such.
After I flew back from Kansas, they took forever to get back to me. I followed-up with them twice but didn't get a response.
All in all, all personnel were pleasant. No curveballs, just straight questions about skills, portfolio.