For the SDIT role, they focus on how you think and the basic fundamentals of Data Structures: linked list, search, graphs, tree.. etc, and some behavior questions. I have a couple of interviews at the Redmond campus, and at the end of the day, I felt I've been brain picked for a whole week. Normally, the on site interview will be conducted by at least three person, and at least two of the three will give technical interview where the other person will give behavior questions. Some of the questions are not difficult, but it's hard when you have to write a program in the white board and within certain time limit. Good luck!