it does cover the whole world, but not all of it is in high resolution. a good chunk of the US is also in low res, but large "strips" of high res coverage makes viewing some runs possible. Its free at http://www.keyhole.com
, or search the web for "Google Earth 4". How much you can see depends on the resolution of where youre looking at. For example, the Crested Butte area has a big chunk of high res through it, so you can see it snowmass, highlands, and buttermilk all very well. But just 30 miles downvalley, Gunnison is still in low res so you can see much.
It is a very incredible program, and i think it will have more impact in years to come than what we see now. definitely check it out if you have the option!