We've been half term week last two years (no choice - work in school). It's busy, but not so much that it becomes a problem. Weather Feb 07 was ok - skiing at top of mountain was good, although not mid-station downwards. It just meant that we had to come down last bit in gondola at end of each day - not really a problem. Feb 06 was fantastic - deep snow all way down.
It does tend to be more expensive though - like all school holidays