I play on one of the lighter servers, and I frequently see people in the starting areas say they're re-rolling from (full server) because they're tired of the constant wait. I think it would be a smart idea to allow people to move established characters to a server that has less population than the one they play on, for a few days at least. This would allow the server populations to smooth out a bit, so you don't end up with a huge imbalance between the full and light servers. Better that the population correct itself a bit now, rather than possibly end up with some truly dead servers down the road.