Here's what was good about Cata, IMO:
Badlands revamp.
Silverpine Forest revamp.
Deepholm.
Starter 5 man difficulty (but not the instances themselves)
Well of Eternity (I know, scripted, etc. I still enjoyed it)
A few Firelands bosses.
And uhhh... yep, that's about it. Everything else seemed like a handbook on how not to create an expansion. I spent most of the expansion unsubbed, and even that wasn't enough.