I went to Valmorel for 2 weeks as one of my first skiing holidays. It has a great atmosphere, and for a purpose built resort the architecture is quite pleasantly 'chocolate box'! The Skiing is quite sufficient for most intermediates, but the low-level of the resort makes it especially susceptible to poor Easter conditions. The new high-speed covered chairlift has helped deal with this by getting you high, quick (and back again), and the many snow cannon make the cover last that bit longer. The resort has a great little area for beginners, with its own slow charlift and drags - providing a nice safe area, off the main pistes. Valmorel is more of a locals resort than some of the others in the Tarentaise, again adding to the 'French' ambience. I would expect that it would be a magic place to be at christmas. Valmorel is also quite cheap as most of the accomodation is good-quality Self-catering.
Overall, Valmorel is great, but the snow levels can be a bit problematic.