I've played all classes at least up to level 50 (most up to 60 at least) except Warrior. :S

Warlock is fun, but you have to remember that if you hate having to manage a pet at all (like you hinted at with Hunter), it may not be the best for you. Still, give it a try. Demonology is super fun (even though it's pet-oriented) and so are the other two trees. My Warlock is 63-64 and I've tried all three. :D

You've played a 70 lock :)

And yes, yes, yes. To all three. But the other classes are more fun.

You, sir, will no doubt fail at lock as you fail at life!

And to your questions, I say:
1. They used to be more fun (in vanilla) then they were in BC. I did not play laramie much at all in WotLK so I have no idea if that still holds true.
2. The locks in raids I have been in seem to be in the middle of most DPS recounts. As for PVP, each spec has it's strengths and some huge weaknesses. I guess the level of power is really more up to the player though. They are a hard class to be great at but an easy class to be good at, if that makes sense.
3. I always thought Aff was a well designed tree with lots going on to keep you interested. I never liked Demo (way to reliant on pets) and Destro (IMO) is just spamming nukes, therefore kind of lame.

On a side, yet related note... You should roll a troll lock in cata, as blizz has decided to give trolls locks as a new class (the statement was made about a month ago). A troll lock will pretty much own IMO.

On another side note, not at all related to this post, HI SIR!!!! I MISS U!