I gave up Mint after running into a lot of bugs in the XFCE edition. KDE should be be better, but Mint's focus is has always been Ubuntu.
I am now back on Mandriva XFCE: family machine on 64 bit, work laptop on 32 bit. I have had no real issues with 64 bit, except with Flash (solved now). My (7 year old) daughter got a bit confused by software installation when the GUI installer showed both 64bit and 32bit versions of some packages. The biggest problem is that packages or binaries obtained from outside the repos may be 32 bit only (and that last point definitely applies to Ubuntu too).