Having kind of an indifferent reaction to this. For one thing, it's really weird that a release date is set before anything's gone before the cameras.
Secondly, i think everyone was expecting this to end up being released either late this year or early next...but pretty much the very last week of 2011 - holy guacamole! A year and a half away? I mean, don't get me wrong - i don't wish the film to be rushed but at the same time, that is really way too long - especially given the incredible wave of popularity the Muppets have been riding...wait that long and too many people might already be bored with the idea. Strike while the iron's hot! I mean, you could prepare a whole other Muppet movie and get it out before this one ends up shown.
In between the hyperbolic title and a ridiculously long wait and that high profile a date, the film's almost dooming itself to disappointment because it's creating a certain level of hype that may let people (Muppet Freaks and regular folk) that end up feeling let down because it didn't live up to it. (Don't mistake what i'm saying here - i expect this to be awesome but a project can only get hyped so much that at a certain point, the final result can't match the hype)
Besides - it's the Muppets! Yeah, there's lots of associations with Muppets and Christmas but why not choose an earlier holiday that's both soon enough to be realistic if things take longer than expected but not so far away that the wait does more harm than good while at the same time being a very Muppety date...like April Fools' Day?