Obviously with the reduced pricing a lot of people flock to the high pop servers like area 52, stormrage, illidan etc. But there's plenty of realms that are med-high that people transfer to.
It's so funny seeing some people whining about dead servers they play on then people whining about full servers and queues. Yeah, I bet it sucks if you can't log on earlier and you have to raid, but that's what you have to deal with. The pop on stormrage has been steadily increasing for quite a while, even before the reduced xfer prices.