Firelands and Molten Front dailies were pretty great, but I wasn't playing when that patch was current content, so most my experience there is mostly after the fact.
Dragon Soul being mostly shit, especially with the clusterfuck that was LFR on release turned me off the game until shortly before Mists. I didn't have the best time with the initial raids either, though that's more a personal issue than with their quality: I failed a tank trial early on, and didn't come back until Dragon Soul opened (which, as mentioned, was another short stint for me).
So I kinda missed out on the best part of Cata, but whatever. I did get to enjoy the "brutally hard" heroics at the start: those were fun, especially getting the dungeon meta achieve within the first month or so.
Overall the expansion was certainly flawed in more ways than it succeeded, but it wasn't all bad. I would sill rank it second from last, with Warlords taking up the rear (raid quality doesn't excuse the other failings).