Also known as "UI, but UI is too short of a post title, since we all know the title must be more than two letters. For other examples, see 'FU' and 'H8', neither of which make particularly great titles, due to saying very little except some sort of generic dislike." On the other hand, run-on titles aren't so great either.
Does WoW have a good baseline UI? I have no idea. Maybe? Perhaps it is what scares away those 30% who don't get past level 10. Or those 30% just don't like MMOs or whatever you prefer to call WoW.
But who cares? WoW has a customizable UI. If it doesn't get the job done, we change it. Can't heal? UI! Can't tank? UI! Can't use the AH? UI! Can't DPS? UI!
I don't much like this approach. It's not merely a bandaid; it's a lie. Yes, a lie. What does a custom UI say? Well okay, it could just say "I want something prettier" and that's fine. But beside that, what does it say?
"You can't play this game well enough and the problem is not your skill or the game design; the problem is that you're not looking at it correctly."
Now maybe I'm crazy, but shouldn't the default game UI be the correct way to look at the game, or at least sufficiently close that everyone (+-100%) do not feel the need to change it? Can you imagine a car like that? Oh sure, all the stuff works, and you can customize it, but maybe the windows should be at eye level, rather than foot level, by default. Of course we could drive with the windows that low, but the angle would mean a really short visual range, so drive slowly!
Healers like to whine. About how they are fighting the UI rather than playing a game. Psh. Everyone is fighting the UI. Every class has the information it needs not where it is needed, which is to say, where we are looking. Why are my cooldowns hidden away at the bottom of my screen? Why is the health of my party over on the right? The action is in the center!
We could say that these are skills to learn. Well sure, we can go with a "learn the UI" approach and block extensive customization. That sounds awful, right? Maybe. Or maybe not. Most games use this approach. Such as Starcraft 2, which I hope is an interesting topic for you, because I'm going to be talking about it a lot (or I might suddenly stop after this post, it could go either way).
Starcraft has a pretty awful, inefficient UI. If I want to build a marine, how do I do that? There's no "build marine" button. Instead I have to find a barracks, select it, build the marine. The particular barracks matters as well. It's some crazy complex stuff (not really, but let's pretend for the sake of exaggeration). I'm attacking over here (lower left), but building over here (upper right), see the problem? Just awful. But.
That's the UI that we all use. That is what we learn. We can tweak it slightly with some hotkeys and control groups, but none of us have a fancy light that pops up and says "carrier group spotted in minimap, build marines." Which may be a good thing because I'm not sure how well marines counter carriers. Maybe vikings would be better? Pretend I didn't go on that tangent (I wonder what this button labeled "backspace" does).
There's another layer to it: the actual game. The UI is not layered on the game, it is the game. The barracks builds marines. Let's say that again: the barracks builds marines. The build unit menu does not build marines. There is not so much a UI that I fight to build marines, but the game, and that game within the world simulation that it simulates. Of course with careful use of hotkeys and rally points players can halfway imitate a build unit menu despite using barracks, but ultimately the barracks builds the marine, so I have no choice but to be aware of the world and what is going on, rather than the UI. If that barracks is on fire, I do not have an alert of burning buildings, but instead the place that builds marines also can burn, so again, I am not playing the UI, but the game.
I guess what it ultimately comes down to is this: When I see someone playing, I want to think "wow, he's really good at this game" rather than "where did he get that UI?"
You may now commence commenting about how you healed hardmode something with the default UI and I'm just bad.