I joined Blog Azeroth. They have this nifty shared topic thing, and one of the currentish topics is "How will Cataclysm change your game?" And there's the original suggestor's response.
Well, Cat has already changed my game. From the moment they said "hunters, no more mana for you," I realized I needed to have at least one more 80 so that if hunters get completely boned, or if I hate focus with the burning passion of a thousand stars, I have other options. Now, I'd already gotten an RAF account and was leveling a druid/priest pair, and the Cat changes just offered more incentive. And now, Lyllea (my priest) is my main, Garetia (my hunter) is my lvl 80 alt, and I've got a druid, a pally, and a DK slowly wandering through Outlands, just in case priest healing gets gimped. I don't think it will, but it doesn't hurt to be prepared.
As far as the new stats, I dunno. I think it will make my game slightly more inconvienent, since it's sounding like dps caster gear won't overlap with healy caster gear anymore, and that means two full sets of gear (three if you count pvp). Not so sure I'm thrilled with that.
More than anything, Cataclysm just provides me with more incentive to get things done. I am a procrastinator of the worst sort, so having a deadline helps me get things done.
There are things I'm really looking forward to, like rolling a warlock Alliance-side. I'm not a big fan of humans, and well, gnomes squeak, so warlock's the only class that is horde-only for me. I should probably figure out how to free up a character slot for that.
I'm also looking forward to the zone updates. Goodness knows, I've no desire to level through the same zones over and over again, and yet this is what I've been doing. The dungeon finder helps a bit with this, but let's face it, you have to do something while you wait, and there are only so many games of Peggle I can play.