6800 is da bomb. It's a return to 6600-level shifting performance and beyond, 6700 and the like suffering from excess cable friction especially if combined with lousy internal cable routing.

The front der can be finicky to set up, but other than that it has restored the faith in shimano I had lost with 6700. Working on so many poorly shifting bikes with 6700, 7900 got me depressed, even though internal cable routing (kill it with fire!) had much to do with it.