The process was relatively long on the day of the actual interview, with 6 people for ~1 hr interviews from 11:30 am to 5:00 pm with only very short breaks. However, everyone interviewing me was nice, friendly, interested and also asked well thought out questions. You should be prepared with behavioral interview answers since they all did ask behavioral questions.
I prepared for about 2 weeks prior, both for the behavioral questions as well as understanding Pfizer (the company) and the therapeutic area, so that I could ask pertinent questions. I also came prepared to ask questions of them to determine if we were a good fit.