Well, I'm certainly hoping that we'll see more about Skill Challenges in DMG2...
When I first read of Skill Challenges I had assumed (or at least was hoping) that they would be a way to make non-combat encounters as (or nearly as) "crunchy" and mechanically tactical as combat. Now, obviously in 4e that's kind of a tall order, but I think they missed the boat simply on the basis that there wasn't really room in the product schedule to provide the number of options for Skill Challenges that where available for combat encounters (powers, different monsters, terrain, dungeon tiles).
4e mechanics don't always (if ever) map directly to the "fictional reality" of the game world. I guess this is most obvious in the combat mechanics, where concepts like a "hit" or hp are really abstract and squares behave like circles. When I (at least) imagine the characters creeping into a dusty and dimly-lit room in a moldering dungeon, I don't envision it laid out in perfect 5' squares, nor that the characters are careful to stay in the exact center of each square. So, sometimes, you have to deal with the mechanics and then puzzle out what the results you get mean, in terms of the fiction (or role-play or story, or whatever you want to call it). The problem is that the DMG Skill Challenge rules tend to give the players one best option for proceeding mechanically, and then unless you have the fiction trump (or obscure) the mechanics things just get boring...
Failure has to be an option. The point of having different skills is that there's going to be some things that a given character is good at, and others that they just aren't. Personally I'm a bit miffed when my character's limitations are glossed over... (Not as much as when I don't ever get a chance to show off what he's good at, but still...) I agree with the idea that Skill Challenges can create an environment where failure is more acceptable than in combat encounters. I think that it's important that both success and failure (and any partial results in-between) lead to fun in the game. As I said before I really lean towards making success a bonus but not overly penalizing failure, but as long as there's somewhere interesting to go from the results of a failed challenge I don't think it matters. Of course, you will (and should) still have the players doing their best to succeed...
So, one thing that stuck in my mind is that every 4e character has something useful to offer in combat. As such "Can we kill it?" becomes the first question players are going to ask when confronted by an obstacle in play. I was thinking that it might be a good idea to have a "backup plan"... And this doesn't have to even be a backup, it might be the first option the players consider before resorting to bloodshed... But, anyway, my thought was to ask the players, before character creation, how they wanted their characters, as a party, to approach the challenges they face in play other than fighting: they can be stealthy & acrobatic ninja-types, political manipulators, con-men, whatever...
{Now: I think I should mention that I'm not fond of the way that class skills have been dealt with in 4e. It's part of the flavor built into the game, and that's OK, but I don't personally feel like 6 trained skills is a lot and I also don't agree with the idea that there are just tons of "extra" feats floating around for 4e characters that the player isn't going to be able to throw at Skill Training without losing out on anything else. As a result I'm planning on house-ruling to allow characters a much wider choice of skills, based on character concept rather than class.}
So, back to the idea of a backup plan, if every character has a t least 2 or 3 skills appropriate to the kind of solution they have chosen, and if I keep in mind that this is they kind of thing that the PCs are likely to (and that the players are going to want to) try then I think we should end up with a lot more Skill Challenges where everybody has something meaningful to contribute. Not that I won't throw other stuff at them, of course...