I went to Vail for two days at the end of February. It was not even close to enough time. This place is amazing and HUGE. Everything the other reviewers say about the back bowls is correct. I could've spent one day alone riding each different bowl.
Vail has everything any boarder / skier could want. Long groomed runs. Powdered Steeps. Cliff Drops. Glade runs. Everything. I enjoyed Blue Sky Basin very much, but as I only went there two days, this is an unqualified opinion. There is so much area to cover two days is only enough to see it all, not to know it all.
I spent my time in CO. just experiencing as many resorts as I could. The next time I do a week, it will be at Vail, and only Vail.