Sun Peaks is a fantastic resort with plenty of runs to keep you occupied for a week or so. For beginners the 5 Mile or Homesteader runs are great confidence boosters, letting you go right from the top of the mountain with only a couple of hours lessons.
For intermediates there are sufficient challenging blues that you can have all to yourself. It is also worth asking a local/Sun Guide or an instructor about some of the easier Black Diamonds, because they are managable for an intermediate skier.
I can't comment on what it's like for advanced/expert skiers - I'm not one.
Of the other activities available at Sun Peaks I can recomend the dog sledding. It's a wonderful half day activity full of fun and laughs.
The only downside to Sun Peaks is the limited number of restaurants. if you are there for a week or more you can easily get through all the restaurants with time to start back at the beginning again. What is available is great (M Room and the Italian restaurant stick out in my mind), but there should be more options in a growing and ambitious resort.
We stayed at the Delta, and have booked again for the 2010/11 season.