Ford has announced a service bulletin for 2011 Ford Mustang GTs with the six-speed manual transmission, to address problems with the clutch sticking to the floor at high RPMs, returning to the normal position only when the engine RPMs drop.
The problem affects GTs built before April 25, 2010. It appears that on those cars--especially ones with low mileage--and it is caused by centrifugal forces at high RPMs that reduce the force at which the clutch diaphragm fingers push against the release bearing.
If your Mustang's clutch isn't returning from the floor after a shift at high RPM, get to the dealer for a free repair.
Sticking clutch or not, I'll still take mine in manual-transmission form.