While I have some issues with the Skill Challenge rules, the best thing about them, which I believe are only partially-stated, is that they offer an incredibly flexible system for players to affect the game environment.I'd add: in 4e it can also be done using the skill challenge rules, provided the GM let's the players take the lead in shaping their response to the challenge, and using early successes to establish the ingame context for subsequent skill attempts. There's no reason, in principle, why a successful skill challenge couldn't even result in the death of a foe.
My experience is too many campaigns become 'how do we fix it with magic' by mid-to-high level. Thus strategy breaks downs to spell selection, more or less. 4e removes most spells, turns some into Rituals, and then goes even further by adding this --admittedly wonky-- tool for doing almost anything in-game.
Trying to: start a war? Open a success trade route? Make your own artifact? Kill a dragon with a folding boat? Why not use a Skill Challenge...
The specifics are still buggy, but the idea that you can produce almost any effect in/on the game is golden.