I can help you a bit because I'm currently on exchange at Hokkaido University in Sapporo.
First off, the actual exchange program is only alright. The Japanese language classes have very good profs and are fairly challenging, but the course selection outside of them is very lacking. Some courses are either taught in English by Japanese professors (who tend to not be very good at the language), or are taught with the purpose of teaching English to the university's Japanese students. Both of these kinds of courses tend to have very low workloads and somewhat useless subjects like Sex and Gender Studies or Tourism Studies, and probably won't teach you much. There are more specialized courses for Science and Engineering students (from what I've heard), but a lot of the general arts courses suck ass outside of the language courses. As an upside, the workload is pretty low and it's possible to make 2 or 3 days a week devoted to skiing as long as you keep up with school.
On the other hand the campus is excellent and accommodation is inexpensive. The campus is located very close to the center of Sapporo, and has wide open areas of green space between most buildings, along with many beautiful trees and a river. It's great when it isn't covered in snow. Dorms are standard but affordable.
Sapporo has easy access to a lot of great skiing. I spend most of my time skiing Rusutsu, which is about a 2 hour (free) bus ride from Sapporo. It's Hokkaido's biggest lift system, and has excellent tree skiing, some big cliffs and a "sidecountry park", which is some jumps and drops built into the woods with natural landings. There are a ton of other areas accessible from the city as well, like Teine or Kokusai which are closer but much smaller. Niseko is pretty far and expensive to access, not worth it for a day trip.
Sapporo is an awesome city. Most of the buildings are boring cubes and it's kind of ugly overall, but there are lots of nice parks and mountains throughout the city that break up the monotony. Sapporo Station and Odori have high end shopping and restaurants, Susukino is the biggest red light district outside of Tokyo with thousands of bars, great ramen and curry restaurants, and is totally safe to walk around at night. Great place. The weather is ok. Summer is consistently warm but not hot, and sunny, Fall has cool temps but stays sunny and has gorgeous colours, and then it snows almost every day from late November to March. It's switched to rain now.
Hope that helps.
