Aside from the terrain and zone changes in Cataclysm, it's held my attention on one Alliance character to level 40. Horde side, I'm only to level 20. I picked up a Battlechest and time card right before Black Friday, so I really didn't devote much time to it. Played with a friend from another state for a bit, played a little with a couple my Friday Night friends, soloed for a few hours, nothing too strenuous. It had been a couple of years since I'd played, and my prior account had been locked for one of their imaginary, semiannual "security breaches," so I had to make a new account. Anyway, it didn't take a whole lot of time or effort to get that far. A lot of stuff that I remember from pre-Cataclysm is either gone or seriously nerfed. It's totally repetitive, though.
I wasn't ever really much for dungeons and large-scale teaming, but there was a dungeon in Westfall where you end up killing a pirate at the end. Post-Cataclysm, his daughter is a "big bad" in that zone. I thought that was a nice touch. At least the writers are doing a decent job on the game.