i gave up my cannondale supersix evo racebike for a santa cruz stigmata, and don't miss anything.
one wheelset has 30c slicks
other wheelset has 40c nano tcs
i'm lucky that my knees can't handle anything too technical, so don't have the need for an mtb. anything stiggy can't handle is something i probably shouldn't be doing on another bike anyway.
if my knees weren't so wonky, i'd add a f/s 29er to the mix for the 2 bikes to rule them all.