Here's what I found immediately relevant to myself:
310 Mounts trainable - Not clear if this is related to all players (have 310% mount and not). To me it has two possible interpretations. First, I have a 310 mount, and if I can train and convert all my mounts to 310 speed. Second thought, like the Cold Weather tome, you could send this to your alts and get them the 310 speed. IMHO, Blizz don't waste dev time if it's option 1. Having gone through the holiday achievement, it should be given to me. If it's option 2, I could see a definite need for it, my dk could be my herbalist and go around gathering mats for me on his 310 dk mount.
It certainly is happening, but it will only be purchasable by characters who are level 85. Players who already own a 310% mount will be 'gifted' the training, and it goes without saying that once the skill is learned all flying mounts will become 310% mounts. That's the current plan at least, and we don't plan on offering any further speed increases to these mounts. (source: BlueTracker)
No plans to force wand usage - Personally, I interpret this to mean that mana will not be an issue in cataclysm. In Vanilla, leveling up, the wand was my best friend (curse, corr, wand). Now it is only used if/when silenced.
Gems will convert to new stat - Considering I just spent 600g on gems for my PVE gear, I wasn't excited about buying all new gems with the new stats on them. Just hope for a equitable conversion.
haste = more ticks on channeled spells - This is Glyph of Quick Decay applied to my channeled spells also. Stack more haste for more dots.
Pollution: "On the third (?) hand, you’ll be cleaning up the toxic waste in Gnomeregan if you can retake it! " - Keyword here is "IF??". So this will be a world event, like whatever that thing I missed was. Opening the portal??.. Will this be a horde vs Alliance thing? It sounds like it will be possible to have some servers who haven't reclaimed Gnomeregan and some that have.. I'd like to see some of the fabled gnomeregan losttechnology snuck into the game as orange, er Legendary items.
CC in PVE viable, yes - This will make for some interesting fights. I am guessing the corollary will be not as much AOE in fights, as they will be running off after that lock aggro'd him.
Stuns diminish - When asked specifically about demo locks and getting another CC to deal with stuns, they responded back that the impact of stuns will be diminished. Interesting. OK, going back to CC in PVE, does that mean we'll have other problems? As a lock, I really hope to see a nerf to rogues stunning me without being in melee range. Running along in AB and I get stunned by some unknown source. It disappears and I can move along. Sort of like I just hit a particularly tough pothole and knocked myself silly.
At this point, all I can tell is game play is going to be different. With the known shard changes, and dot changes, and even my role in a 5/10/25 person group is going to dramatically change. Heck, maybe I won't simply be the candy and closet guy.