A day at Sumikawa was supposed to be the sideline on a 3 day trip to Zao but ended up being the highlight of the trip, besides our penshon Mama's apple pie that is. It certainly helped to have beautiful weather all days and superb views of the surrounding hills. Another big plus was the friendly and relaxed lift staff, no grumpy farmers to rope off everything interesting. There were plenty of natural features to keep this smallish resort interesting for a day at least and the park facilities were excellent. The boarders and skiers hitting the jumps were definately a cut above your average resort trier. I think this must be the hill of choice for Sendai's park bunnies.
If you're in the area it's definitely worth a day but a bit small to keep you interested for much more.