skiing
The skiing is great, the resort is filled with open flowing runs. The most enjoyable aspect are the off-piste powder hunting, easily accessed by screeing from the lifts. The Roca Jack, Condor and one new one the name escapes me are the world's only sling shot lifts aka va et vient. It's not a regular chair lift, it actually looks like a giant slingshot. There are runs for beginners and pros alike, but timorous intermediates may find they spend more time in the bar / restaurant than on the relatively few slopes that are prepared for their ilk. Incidentally the word "queue" doesn't exist hereabouts.
Backcountry skiing
And snowboarding is very possible. you'll find great open powder slopes right by the road. competition from other backcountry hikers is non-existent. bring appropriate avalanche rescue equipment. beware that most of the runs is concave and gets very steep at the top. be careful. you can supposedly check conditions with the resort before setting out. they operate heli-skiing.
Pool bathing
There is an outdoor pool in the resort. it is heated through the mountains own geo-thermal heat, and it's a relaxing alternative to skiing. and was populated by the boys and girls of mtv brasil on my last visit. not exactly relaxing, but definitely an alternative to "feeling the powder of the andes".
Helicopter sightseeing
Seeing the altimeter in 5 digits when you are still on the ground sets the tone nicely and aconcagua close-up is quite something.