I'll provide input on the following classes:

Priest - Probably my most hated character. Terrible healing all around (direct, aoe). Terrible dps. The only reason I keep it around is I am collecting t2/t4 gear for all my chars, plus priest gear is cool looking. Oh I guess mass dispel is kinda nice.

Shaman - my favorite healer by far. never was a fan of shaman melee though.

warrior - arms spec is great, he does good dps once you get him a nice ilvl 2hander. kinda hard to get used to since you really need to be on top of overpower, the video fx of isboxer helps as i have a small box with the overpower skill in it that is right next to my tank's threat meter, since i'm always looking there i can easily see when it pops up and i have to activate, same for execute.

feral druid - super easy to macro, goes well with the warrior. mine sucks because there is no leather gear on the AH ever, i am forced to level leatherworking to gear my druid. i like it though. tried to macro a boomkin last year and failed miserably.

hunter - i found that you are limited to beast mastery spec, since that is easily macroed vs marksman where you really can't macro chimera too easily without taking a massive dps hit. plus you'll get a cool looking pet.

paladin - i used to hate my ret paladins. yesterday i activated one at level 83, found out he was super easy to macro and put out good dps. i now love my paladin again. can't wait until he is 85.

rogue - not very impressed. super easy to macro, but even though he has ok gear, his dps still isn't that great. he's kinda "meh" to me. only in the group to soak up t1/t2/t4 rogue gear and cool looking weapons to transmog.

dk frost/blood - always impressed with the blood dk tanking ability and dps output, and the frost dps output. frost was kinda like the warrior in that you have to set up video fx to monitor procs (or use procmon from jamba).