Like Syp, I'm a bit down on the beta these days. I'm pressed for time and I've got so many games I'm playing where I actually get to keep my progress that it doesn't make a ton of sense to spend time on an unfinished version of a game where the characters will be wiped in a few months.
I didn't apply for the Rift beta, even though I'm nominally watching the game. I might try a pre-release open beta as a free trial equivalent, but I'm not interested before then. I was in the beta tests of both TBC and Wrath, but I wasn't invited to test Cataclysm and I don't regret having missed it. There will be plenty of time to see how things turn out as the dust settles over the next year.