I was one of the few people who interviewed for two different positions (both for PM and TS). I initially applied for the PM position, but during my phone interview, the interviewer suggested that I may be a better fit for the TS position, and when I flew in to actually interview, I found out that I was signed up for interviews for both positions.
I applied online through my school's career website. After I applied through the company website, I had to take a personality test. After they reviewed my application, they set up a phone interview for me. During that phone interview, I got to talk to a PM, and it was a very thorough interview.
Phone interview went really well, and they told me that I would have to take a standardized test first before I move on to the next round. I found out that not all applicants were required to these tests before they flew in to Madison, so that will really depend on your case. The standardized test wasn't too difficult. It's a lot easier than SAT, but similar format, so take a deep breath, and just focus, you will do fine.
After I took the test, they took couple days evaluating my test scores. Then I heard back from them saying that I am finally moving to the final round of interviews. I flew in for the final round. The company environment is really nice, and they always dress in casual clothes, which I loved the most about the company. If you are interviewing for PM, you will have an overview of the position, case study, presentation and the test if you haven't taken it already. If you are interviewing for TS, you will have an overview, case study, and the test if you haven't taken it already.
I had 2 overviews, 2 case studies, 1 presentation, 1 coding test (the coding test didn't really count - and they told me that it was just to see if I would be a better fit for PM/TS), and 1 2-minute test. Interview process was pretty good, and they put me in a really great hotel, so that was a great experience.
If you go prepared, and if you really think the position is something that you would like, you should do well on the interviews. Case study questions are very behavioral, so be prepared for that as well.