When we're not madly AoEing, my new computer gives me up to 70-80fps in Ulduar, an instant (rather than - literally - 5-10min) load-in time for Dalaran and the ability to run (and tab out to) other programs running in the background without the 5min wait.
I've also discovered that my character's shadow isn't actually a small dark circle on the ground, which was rather disconcerting at first, but it's definitely growing on me - my drake flapping against snow was a good couple of minutes' entertainment.
Hooray for a better WoW experience!
(In case you're wondering - the settings for my old computer are fine for raiding; y0u won't miss any important boss spell effects. You could even lower the settings further than what I had)