Well, I've just booked a car through for a skiing week in CO, I'll report back here on how it goes.

With regards to using my US license, I called and was told I'd have to use Budget as the supplier. This increased the cost by about 30%, but was still half the price of booking the same vehicle directly with Budget locally. They were happy for me to pay with a US-bank-issued VISA card, though their online site wouldn't process that - I had to call (that problem may have been independent).