• Warriors got a big change to rage generation that, as far as I can tell (there's a lot of math involved) gave a nerf to anyone carrying around a two hander. Rage was normalized, especially on crits, so people are reporting from 3-4 to up to 10 less points of rage per crit damage. Of course, as gear gets better, so will rage generation, but the warriors aren't thrilled.
• Mage AOE took a hit, as well-- right now, AOE hits any number of mobs in a certain area (hence, "area of effect") for the same damage. After the patch, AOE will diminish (see point number 6) after a certain number of mobs-- beta testers are saying it's around ten or so. I didn't think this was a big factor (because when are you really fighting more than ten mobs, but I was proven wrong tonight in ZG, when we found countless numbers of panthers and spiders and the AOE was necessary to finish them.
• Hunter pets got "normalized" (more math-- anyone want to try explaining this simply), which means Cat pets will see a drop in damage and Bears will see a small gain. Also, Hunters aren't thrilled that The Beast Within (one of their BC skills) was nerfed to a 10% damage bonus from a 30% damage bonus. But they aren't crying nearly as much as the...
• Druids, who got hit big: there will now be a one second cooldown for all shapeshifting abilities. Also, feral druids were very excited to be able to use consumables (and weapon procs) in bear and cat forms, but the devs say that was apparently a bug, and it's not happening in the beta. That has got druids torn up more than anything else, so there is QQing aplenty over on the druid forums (though there may be hope yet).

Via WoWInsider