Worse, skill challenges encourage the "I diplomacize him" style of play where negotiation and conversation are condensed down into a single diplomacy check made by the most charismatic character in the party (inevitably being played by the least charismatic player at the table...) In fact, it is my obsevation that it these rules-focused, munchkin players who are skill challenges' biggest fans.
I've seen this kind of behavior pre-skill challenge. I don't think skill challenges should be blamed for what might be a problem with how skills are implemented.
Not only are skills considered rather boolean (you either succeed or you fail), but the tendency is to max out one skill rather than have a "well-rounded" kind of character. There isn't an incentive to play a mildly skilled player, for example.
So what are skill challenges supposed to accomplish or remedy in the D&D game? Is it to get all players involved specific non-combat scenario/encounter? I am personally all for that, especially when one player is hogging all the screentime with his Diplomacy or Stealth, while the other players are bored, watching TV, or playing on their iPhones.
The errata eliminated the requirement that all players participate in a skill challenge which defeats that purpose. The real goal (which Stalker0's Obsidian system addresses) is that characters without the appropriate skills should be allowed to participate and be rewarded.
I don't think the solution is to have games designed only so that Player A can shine while Player B waits, and then have another scenario for Player B to shine while Player A sucks it.
The other goal (maybe unintentional) of skill challenges is to soften that boolean effect of one roll to resolve a complicated situation. This either encourages players to choose their one good skill and thus turn the whole exercise into "I Diplomacy him again, and again, and again" or you might have to say "you can't use Diplomacy again, choose another skill" which might feel artificial.
I had thought that perhaps the die roll skill system could be removed and replaced instead with Skill Encounter powers. Perhaps a "Use Diplomacy Successfully" Encounter power could force a player to decide if convincing the one bandit to come to their side is more important than convincing the bandit leader from looting the church, for example. (I had wondered if a Daily Skill power would have been the way to go, but that might convince players to return to a 5 minute work day.)