I'm a fan of Synergy, but it's too buggy for me to seriously use. It breaks highlighting on the server side, and it breaks the AutoType features in KeePass, among other stability problems (i.e. sometimes it makes a shift key be stuck down...).
I'm curious if there are tools that do anything similar out there.
However, unlike Synergy, cross platform usability isn't a requirement. I rarely use anything other than my Windows boxes; and those are all I need something to work for.