The one thing I notice about skill challenges and the largest problem is
one of exclusion. PC's that do not have the skills to attempt a roll with
anything less than close to the optimum bonuses just end up aiding
someone else or sitting on the bench to avoid dragging down the team
with a poor roll.
4E overhauled the classes in a major way to help ensure that
every PC could meaningfully contribute to the action. As far as combat
encounters go I think the goal was achieved, but non-combat encounters
didn't get the same treatment. The three failures baseline for failure is the
equivalent of saying that once three hits are scored against the party
before they can score five or six, the combat is over and the PC's lose.
In a combat encounter, every PC has a variety of actions that
can be performed each round. All classes were given powers that
are useful in the encounter. Powers that, to me, make no sense
as to why they would work in certain situations simply work
because the overall goal was to ensure useful actions for everyone.
In addition to these powers and attacks, are improvised stunts that may
be attempted with varying degrees of success. My point here is that
combat isn't restricted to a static menu of actions (no matter how much the character sheet makes it appear so

)
but the skill challenge mechanics as written ARE structured that way.
Even if we removed stunts from combat, every PC would have a
fairly decent list of actions to perform no matter what the circumstances
of the particular fight happen to be. On a skill challenge based on social
and knowledge related skills, the jock types help the party most by sitting
out of the encounter and letting the brains handle everything. This would be like having those skilled at diplomacy sitting out of combat because they would be a liability to the party and couldn't help.
I like the skill challenge concept. A sequence of events moving at
a quick pace, with success hinging on some key die rolls that isn't combat
is a good thing. The system needs to allow for things like stunts and improvisation
to bring the inclusiveness level up to the same level as combat encounters.
Simulationism was trampled to death in the name of equal participation in
combat, why not apply the concept to non-combat encounters as well?