Mike Mearls wrote one of those great articles that so typical of him that reveals that as much awesome 4e stuff we see, it's just the tip of the iceberg of his understanding of the game. It's about skills, and you should go read it if you haven't.
Since I show my love through graffiti, I'm going to suggest that the idea is really, really good, but I'd tweak it a little bit in play. For those too lazy to go read, Mike proposes that skill ranks be broken down into a descriptive ladder:
And that the DM should use those guidelines for setting difficulties, such as "It would take an expert climber to go over this wall". If you have the skill at a level higher than expert, you don't bother to roll, you just succeed. If you have it lower than Expert, its out of your league. If you have it at expert, then you roll against a DC of 15 to see if you succeed.
This is pretty slick, and because it explicitly removes the "+ half your level" element of the skill rolls, it makes skill difficulties feel more coherent (rather than requiring EPIC WALLS to challenge climbing at level 25). Mike also slips in a nice trick whereby player cleverness and planning can change the difficulty category of the check rather than give themselves a modifier to the roll. Very slick.
Admittedly, there are no guidelines for how to determine character expertise, but that's a two line rule - Everyone's a novice at everything, everything you're trained in you're a journeyman at. Each feat bumps it one step. If you want to support epic chars being awesome at everything, then characters get an-across-the-board bump at 10 and 20. There, done.
Anyway, I want to call it out as a nice tweak on things, but also as one destined to disappear. If Mike could convince the Character builder to support ideas like this, I would be SHOCKED (and utterly delighted). But I'm intrigued because - unlike most web mods - it's not impossible that it could be supported. I'm going to keep one eye on this, just to see.