Very often when you say a rule covers something, it is true by the letter, bu tthe "coverage" is so general and generic that it is actually more fluff than rules. Saying "you can do other things than roll skill checks in kill challenges" is not the same as having rules to arbitrate how to use attacks and powers. Following a rule like that is pretty much the same as improvising. It doesn't answer the question "What effect does the ability to fly for one round have on a mountaineering skill challenge" or any of ten thousand similar questions. But you are correct by the letter, and arguing the point doesn't seem to lead anywhere, so I prefer to not reply until you called us out on this.
I agree, but I don't think there's much you can do (other than exhaustively detail mechanics for every possible action a character could take, but that approach has its own pitfalls). If you want to resolve actions that characters could conceivably take with simple mechanisms, you're going to need to lean on someone's judgement.
That's why I don't think they need to spell out what you can accomplish with an ability that lets you fly 100' or so in a few seconds. The fictional situation + simple guidelines aid the DM's judgement. Maybe being able to fly 100' will end the skill challenge in success. Maybe it's just one success. Maybe it will cancel a failure. Maybe that will allow the PC to use one skill over another.
What I find missing is good advice: what should be a skill challenge? what is the scope of a single check in the game's fiction? when do you call for an automatic success or failure? what if the conflict that's driving the skill challenge simply ends? etc.
I would like it if they had checklists for each of these questions, e.g. "Look for these aspects in the game's situation: a conflict between the PCs and NPCs or an active environment; a level of abstraction that means the dice are going to have to act as "oracles" to determine details about the situation; and a conflict that can't be resolved in one or two simple actions. If your situation has all of those features, you should think about running a skill challenge."
(I like procedural rules.)
My personal experience in playing through Skill Challenges is that they felt artificial, sor of a game inserted into the game. Normal rules of behavior didn't apply any more. And at the same time, the mechanic forces you out of the game: You have to meta-game or you fail.
Normally, when facing a challenge, everyone pitches in towards that common goal. In a Skill Challenge that will led to failure, as every "helpful" effort that doesn't result in a successful dice roll counts as a failure, and you can't afford them.
Suddenly being forced to say, "I don't know what that is" can cost the party. Better to sit empty headed and close mouthed than even try to think of something, try to see something, try to recognize or remember something.
So you have to look at your character sheet and say, "My character isn't trained in that skill, so I'll just have a seat over there."
That turned me off more than anything.
But that, I see, is a problem with the implementation, not with the concept.
The rule I use - for all checks in and outside of skill challenges (including attacks) - is this: when multiple characters are attempting actions that have the same goal, I call for only a single check and let up to four other characters lend aid. The character who "rolls" is the one who's most involved in the action's success or failure.
A few examples:
* A group attempting to sneak past a guard will have the noisiest character (the one with the lowest modifier) make the check. A group on watch will have the most perceptive character (highest mod) make the check.
*A group of characters trying to convince another of something will have the one who actually makes the argument make the check (which could be the 7-foot-tall Iron Wolf barbarian, standing with arms crossed and eyes staring daggers, instead of the fat, mouth-breathing city dweller who says "I would really like to avoid any trouble.").
*Two guys trying to put an arm lock on an ogre will have one make the check and the other aid. Who makes the check is a little more complicated because it depends heavily on the specifics of their action; it might be the strongest, or the "best", or the guy who's in the best position.