I'm basing this solely on the trail and dog park as I've never skied on the hill.
My two main uses for this park is to let my dog play and for running.
The dog park is very well maintained and under-utilized I think. Parking (about 20 spaces) is nearby which you can access through Don River Blvd. which is on the south end of Sheppard just east of Bathurst. The fenced-in area is rather large and shaped like an "8". This is helpful if for some reason, a couple of dogs don't play nice, they can be separated. The dog owners there are quite responsible and clean up after their pets. There are garbage bins at each entrance.
As far as running, it's about 1.25km from end to end but there are an assortment of hills from each end which are good to incorporate into your training program. When the ski hill is not open, that provides a great challenge too. That said, the ski hill probably isn't much for an avid skier. You're probably better off skiing elsewhere.
There is also a park area that has spaces that can be rented if you want to host a large picnic. It's certainly not as crowded as High Park or Sunnybrook Park.