I'm going to be honest: I still love Cataclysm. I know that it has a lot of problems, but I think a lot of the issues people have with Cataclym are that it isn't Burning Crusade (or vanilla, for that matter), and I'm very much an enemy of nostalgia. Especially in comparison to its immediate predecessor, Cataclysm has a lot of things going for it. Class balance is in a better place across the board than it was in Wrath. Even though Firelands was a giant explosion of red and orange visual vomit, it still doesn't compare to Trial of the Crusader's single room. And, even though we've not been amazing at all during any of Cataclysm, enhancement shaman haven't actually sucked during any patch, much less the entire last year of the expansion.
That said, I'm terribly excited for Mists of Pandaria. Part of the excitement is that for once in my life I'll have a horde race to play that isn't tauren as I hate all the other choices, and The Amazing Panda Adventure was possibly my favorite movie from 1995. Another part of the excitement is that Mists of Pandaria is new and shiny and it's only human to love things that are new and shiny. I love some of the new ideas Blizzard has cooked up for level 90 players, from PVE scenarios to companion pet battles. Yes, I was young enough to play Pokemon when it was relevant, but I'm also old enough to not be ashamed of wanting to play it again.
Most importantly, though, I'm most excited for the potentials changes coming to enhancement in MoP. Enhancement has had some pretty glaring issues for a good part of this expansion, even if we regularly remained competitive. Thankfully, some of the changes that came in last week's updated talent calculator look like they'll be on the road to solving these issues when Mists drops.