The Ford GT, Porsche, Toyota and some other manufacturers successfully use cable shift in production vehicles, so smooth shifting can be achieved with the right set up.
Personally if I was going to spend that sort of dough, I'd go the next step and anti up the ~$3K to get something like the Masterhsift system (www.mastershift.com) that has electronic actuators on the transaxle connected to a renote paddle or bump shifter. But then if I was going that far I'd probably go one further again and get a fully sequential transaxle..... can you see how my projects get out of hand really quickly...
Julian