I ask because when I went skiing at Lake Tahoe I got a regular car, and half the roads required chains or 4wd–they wouldn’t let you past the checkpoint without 'em. 20 miles on cheap chains sucks. Anyone know if I’ll need 4wd to get around Vail/beaver creek or Aspen?
In Tahoe I have only been asked to have chains during snow storms and perhaps a day or two later. Until they cleared the roads. Vail and Aspen will be much the same. You will not need chains or 4wd unless there has been recent snow.
Last time I skied Vail I drove a 1980 Chevy Chevette with mismatched retreads. They keep the roads pretty well maintained up there. Except in the case of a very recent heavy snow you’ll do fine in a normal vehicle, providing you’ve driven in snow before.
It’s on a major east-west, I-70. Get a 7 day forecast. If no real significant snow is expected, you’ll be fine. Otherwise, why risk it?
Well, I was trying to book air-hotel-car all at once, and a month in advance, so I don’t know what the conditions will be. I never had trouble with a normal car in Utah for skiing…but at Tahoe (near Heavenly) they simply would not let you on certain roads without 4wd or chains. I don’t want to be trapped in a little town with no way to the resorts. 
Be safe and book a 4WD. Can’t hurt, and I’d feel safer driving one in winter conditions even if I didn’t need to.
When I went to Aspen a few years ago there were buses running that would take you to all the ski areas in the valley. We had a car but the bus was much more convenient as there were no parking hassles. I would think if anything the buses are better than they were 20 years ago.
As is usually the case, it’s going to depend on conditions. According to the Colorado Chain Law, depending on road conditions you may be required to use chains. If you rent a 4WD vehicle, that requirement would be waived. 4WDs are no doubt more expensive but I would think that if you had to rent one, Colorado would be the place to do it.
As others have said, I-70 is very well maintained. It takes a lot of snow to make them invoke the chain law on it but it does happen.
I spent the first week of the year in Snowmass and Aspen. It snowed hard during our drive back to Denver and Vail Pass was closed. We had to drive way down south through switchbacks and ledges on very, very snowy roads. That and the horrible snow clearing in Aspen leaves me with one conclusion: I’d call all wheel drive a must.
[gloat]Hitting Telluride for a week in March, too[/gloat]
As others have said, as long as it’s not during or right after a big storm you should be alright. Remember, these are tourist towns; the more you’re driving around, the more money you’ll spend. They have it in their best interest to keep the roads open, safe, and clear.
You’re more likely to have trouble getting to or from Vail or Apsen then getting around once you are there. If you’re renting in town, then it’s not a big deal. Use the local shuttle buses to get around. If you are staying out of town and must drive each day, then 4WD makes sense.
Another piece of advice. If you can, avoid ending your vacation on a Sunday. The traffic on I-70 back to Denver is brutal. Or you might consider skipping Denver altogether and fly into the Eagle County Regional Airport. Then you may not even need to rent a car.