You'll be assigned a recruiter that will deal with your on site interview setup. This person gives you further questions to assess where to place you for interviews, because you interview with the particular team you'll be working for if you take an offer. Based on my responses, I was switched from Windows PM interviews to Office PM ones.
Day of the on site interview: You'll go to Microsoft's main campus and head to the recruiting building. There, you have time to play with some of the current products (they had an xbox set up for candidates), enjoy snacks, and mellow out about what's to come. Later on, your recruiter will come out and discuss how the day should go for you, giving you a list of three interviewers and start times for each interview. Additionally, you'll be given a voucher for both you and your 3rd interviewer to get lunch on campus. In between interviews, I was either left at a lounge or the building lobby while my interviewers discussed how I did in their sessions.
My first interviewer of the day was sort of the trainer for the rest of my interviews. He gave me questions to solve and gave lots of feedback so I could learn from my mis-steps, and it was expected that I'd apply criticisms in my later interviews. He seemed a little crabby and made me slightly nervous for the rest of my day, but his feedback really helped out.
Second interviewer: This was my first chance to show I could apply the material taught to me and gave me a chance to meet another employee/get another take on life at Microsoft. While walking to his office, he brought up how he was someone that used to say he'd never work at MS and now loves it. Very personable interviewer. He gave me some questions about my background and gave some incredibly open-ended questions, which let me approach problems from areas I knew a lot about. I was able to bring up things like musical instrument design to answer his questions. After my interview time was up, he gave me his card so I could contact him with any questions.
Third/lunch interviewer: We did lunch in a cafeteria in the building (really good food, and incredibly vegetarian friendly) while we discussed our backgrounds. He was another extremely personable interviewer. We talked a lot about the benefits of working at MS while eating. After finishing, we went to his office to do the actual interview. Again, I was expected to apply what I learned in my prior interviews to questions that my interests drove. My interviewer saw that I have a space background, so I got space related design questions that were almost brainteasers.
After my third interview, the interviewer told me I had additional interviews scheduled, so he took me back to the lobby to wait. My fourth interview of the day was with the person in charge of the team. Her interviewers were target audience focused, so I needed to ask a lot of questions to understand how to best design a product. I was told I had another interview, so we walked back to the lobby while she went to discuss her thoughts of me.
For my final interview, for the first time, my technical background was also examined. I was given a design task to create a product for all ages, which was followed by a problem of encoding information as bits (I probably only got this question because my BS will be in computer science). I got through the questions, and the interviewer told me that everyone was impressed, and that I should expect to receive an offer. Following that, he gave me a product demo of what he worked on, and we got into a conversation about all the ways you could mess with the program. We ran about 20 minutes past the interview stop time discussing it. He walked me back to the lobby, telling me that I'd hear back very soon and calling for a car to take me back to the recruiting building.
Last of the day: recruiter. He asked about my impressions of the interview process and if I had any concerns about taking an offer, should one be extended.
Post interviews: The recruiter was in contact with me to answer any questions I had about the offer itself. Additionally, the employee that gave me his business card answered tons of questions I had about the area. I was even given a call by my fourth interviewer/future boss to make sure any questions I had about the role itself were answered. Additionally, MS was courting students from my school. Those of us with offers/still interviewing were taken out for a night on the company, and I've had multiple dinners with current employees to answer more questions.
Additional interview notes: You will be expected to stand at a white board and sketch out design ideas. Also, verbalize any concerns you have. Do you need more information about the customer? Ask! Do you have ideas that might be solutions? Verbalize them. The interviewers want to know your thought process, and verbalizing can help them catch any misconceptions you may have about the problem.
