I find it very good once modded with the S30 valve for real ales. You'll get about half the keg dispensed with the conditioning pressure and then have to hit it with a spritz of gas to get it going again.
If you like cask then go with KK, if you like kegged then go with Cornie, although there are some such as Saruman who prime their cornies naturally, not sure what resemblance to a cask ale he gets with that though, I'm sure someone else who has cornies will chime in.
KK takes a bit of getting used to and some cleaning up with sandpaper to ensure good seals all around, but once you have it cracked they're great.