For me personally I have found it slightly faster instance leveling (Utgarde Keep is pretty easy once you "learn" the place, you may spend 1-2 hours the first time but you should get it down to 30-40 mins after af ew tries). However, this is INSANELY BORING. I just couldn't do it, my plan was just to grind UtK over and over and over till level 75 but I stopped at level 71 (lol). Now I just kinda wander around, do quests, explore, get diverted extremely easily (spent 2 hours in lake Wintergrasp yesterday) and have fun.

WOTLK endgame is fairly easy, there really imo isn't a huge reason to rush - enjoy the game, have fun, the stuff at 80 will wait for you.