Personally after all the time in the beta, 2 new characters leveled from 1-85(priest and warlock), and 2 characters leveled from 80-85(mage and shammy), I simply thought that the new mechanics sucked. Everyone has the same builds, and so on. Exp was reduced again for 1-60, and again for 60-80. With the new boa gear, and being in a guild with the exp bonus it's possible to get a 55% exp bonus.
There's no real feeling of reward for work done, rather it's handing you a reward because *clap* you were there. To make that clearer, it's because it seems that what little leveling curve there was, is completely gone. The changes are nice sure, but it's not the game I started playing, or was enjoying. Personally for me TBC was the peak in good game play, and leveling. I simply found cata too easy, including the raids.
Anyway most people I've played with over the last 6 years, including people I played with in the vanilla beta have quit. I'm sure I'll get the urge to play every now and then, but for all intents I'm done with it.
--
"For every human problem,
there is a neat, simple solution;
and it is always wrong."
--H.L. Mencken