My dwarf paladin is currently at level 43, getting close to 44. I've been playing the pally for less than two months, and add in the fact I still play my hunter toon, I feel I'm leveling quickly. I feel I'm losing part of the game experience by the fast leveling, which I have mixed feelings about. Many of the quests the pally can do have been done already by my hunter. Most of the quests have been done in the Eastern Kingdom continent. I usually grab as many quests as I can, complete them, and then are directed to another zone in the same continent. The opposite continent, Kalmidor, on the other hand, has only about 30 quests completed. My toon is questing in the Desolace area at the moment, basically skipping several zones in Kalmidor where it can quest because the quest levels are too low.
A big reason for the leveling is the new LFG dungeon finder. I put the pally in que, and after a bit of a wait, go into an instance with four random strangers. Running just one instance can move me up .5 to over 1 level a run depending on if my toon is rested or not going into it. I find I end up running two, sometimes three instance runs in a row. Partially because I enjoy running instances with this toon at the moment, and the fact that if you do a random, you get a goodie bag when you complete it with item upgrades (for the most part). Yep, I'm Pavlov's dog!
I know I can set the game so I don't gain XP. However, due to the fact my hunter has done most of the quests anyway, I don't feel too guilty about bypassing them. I'm considering, if I complete leveling the pally, on going back and going over what I missed. At this point in the game, I want to work on mastering my toon, something I didn't really do with the hunter.