Les Arcs is split over several resourts, named after their height; 1600, 1800, 1950 and 2000. Sitting above Bourg St. Maurice, you can get the TGV from Paris or London, and then take a furnicular train upto 1600 ... no planes and hire cars necessary!
I would recommend the new 1950 resort for its 100% ski in-out, facilities (pools, jacuzzi's) and fantastic luxury apartments. I stayed in the HMC Hameau in 2006, and plan on visiting the Radisson Hotel in 2007 (free WiFi). Les arcs has lots of terrain, with paradiski it's one of the biggest linked ski areas in the world! You won't be disappointed!