This was my first time to niseko (and to hokkaido) and I was more than impressed!
Apart from the pros listed above, I liked the general diversity of the resort (ie. a range of hotels and restaurants to suit all budgets and tastes) and the variety of people there (yes, there were many aussies, but also americans, canadians, brits etc and the majority of people on the mountain are japanese).
I would definately go back and highly recommended it
Haven't been to Kamui in a few years, but made a couple of dozen trips there in the 90s, booking cheap packages that included flight, downtown Asahikawa hotel & bus.
Great ski area for anyone in the range of beginner to upper intermediate; not too interesting for experts. Can be a bit cold if the wind is kicking up, but scenic and typically good snow. Yo-yo'ing the gondola can be a lot of fun, but the runout toward the bottom of