I learned to ski at treetops a couple years ago when our company had a discount there. The lodging there is great, both the "chalets" and the main hotel are both great. The prices on the rooms aren't bad for northern michigan either.
The lift tickets are fairly expensive when you look at what you get for michigan vertical/acres/runs. The lift lines have never been too long, and the hill isn't so high as to need a high speed chair.
The runs are ok, not super challenging but decent. Not bad for a place this size. It is a nice break from the bigger mountains up north and is a little bit quieter if you're looking for more serenity and less punk kids (ha). There is also a nice little restaurant at the top of the hill to grab a drink or two at during the day.
Overall, not a bad place to go. Especially if you use the lodging. You won't miss the crowded mountains and you can relax in the pools or spa as well to complete your stay.