I loved BWL the most personally. As a lore junkie it was great to see a zone that really told a storyline as you progressed through it. It reminds me of the way Deadmines was designed. Naxx was great too, and really felt like they were preparing a seige in there.

I would love to see more zones that felt like actual places rather than "linear instance x" (even though it may be linear anyway, like BWL).

Battleguard Satura was probably the encounter i most enjoyed. Nothing like having a entire raid screaming on TS "omg its coming towards me!". Random fight, yet everyone had a certain role Stunning/taunting/healing/aggro-ping-pong (and yeah, we used swiftness pots there too one time). =)