Bottom line is clutches don't destroy transmissions, drivers do. It's just easier to destroy a transmission with a very grabby clutch... But if you drive with some intelligence and respect for your car (i.e. go easy on the clutch drops and atleast attempt to ride out the clutch between shifts instead of dumping it) your transmission should last just as long as if you didn't get that brand new racing clutch.
Baldcherub - Couldn't agree more.