The in-game penguin pet is now available. If you have already converted your account, when you log in you should receive a special something in the mail. If you are already logged in you will have to log out and log back in to get the pet.

Class-Specific Interface
I don't think it is required. Everyone's definition of required is going to vary quite a bit but very few mods are actually required in my experience.

Building an in-game UI to handle paladin buffs is something we would like to do for Cataclysm (then again, so is "overhaul every aspect of the game.")

It was once a goal to make every class UI the same. Since the DK, and more recently the shaman and to a lesser-extent the druid, and then soon the warlock, we've been moving away from that. (Source)

Gear Score
We actually talked today about adding an item level 300 shirt that did absolutely nothing but mess with mods that attempt to boil down players to gear scores.

[...]  The ubershirt solution would be pretty easy to bypass unfortunately.

Ultimately, we're really not that interested in trying to shut mods like this down. Players will always have the Armory and to a lesser extent Inspect with which to judge other players.

It's not an easy problem to solve. On the one hand, we can recognize that there is value in being able to determine if that guy you are considering for your pug is much less experienced and talented than he claims to be and is going to drag everyone else down and cause other players to leave. On the other hand, the WoW community seems to have become so obsessed with efficiency and so adverse to wiping that there is, in my opinion, an unreasonable demand for player skill and gear requirements even for relatively easy content. It's one thing if your VoA tank is in all blues. It's another if you're asking for Ulduar gear for your Naxx run.

Many players are perfectly reasonable. However we've all run into That Guy who takes any attempt at measuring his awesomeness in the game (gearscore, achievements, dps meters) way too seriously and looks for the same in others. (Source)

Death Knight
Scourge Strike on PTRs
It looks like several players are still posting without reading the entire thread. Until SS is working correctly on the PTR, telling us it has double resists isn't so helpful. I don't want to hit that particular nail too hard because I would hate for players not to report any bugs because they assume we already know about them. But in this case it's not going to be effective -- yet -- to tell us about your SS hits on the PTR.

It's entirely possible we'll end up with e.g. a SS that hits for 80% weapon damage (like Obliterate) and does a lot less Shadow damage per disease. Unholy already ignores disease damage very much at its peril so it's probably okay if this one ability doesn't derive so much benefit from diseases. It will lose a little bit of its synergy with the other +Shadow parts of the tree though. It's just too soon for that decision. We need to see some legit numbers first. (Source)

Shaman
Reincarnation
As I said in the healing forums, we may drop Reincarnation to 30 base, talented to 15. (Source)

Warrior
Warriors in Cataclysm
In Cataclysm you'll get more talent points. That may open up the reality of an Arms - Fury hybrid build. We're not sure if that's something we're going to support yet or not -- we just haven't gotten there yet. For now, we don't really want to see warrior talent builds that go halfway down both specs. They aren't designed to do so elegantly. Arms is really focused around a single slow weapon and bleeds. Fury is built around dual-wielding and "blendering." At the moment, an Arms - Fury build would feel (to us) a little like a Holy - Shadow build -- possible perhaps, but what's the point? That's what I meant by "get both." To do so, you'd have to ignore the spirit of both trees while just trying to cherry pick all the special abilities.

In short, if warriors need buffs (debatable), we are unlikely to do so by making MS - BT the dominant build. (Source)