The thing that I was most excited about was the superior snapshot abilities. Perfect for Time Machine backups, but I'm not really upset with the performance of Time Machine right now.
I agree with Poly about the multi HD pooling not being an issue any time soon. Nor do I see Apple even offering a multi HD setup for anything other than the Mac Pro market.
I'm just hitting the limits on my 250GB drive ůmoving to a 1.5 or 2TB setup should tide me over for a while