I have been using Ubuntu Karmic Gnome since it came out, tho I switched to Mint Helena 64-bit this weekend. I just find it to be a nicer package - more polished and more minty. I also see you just released Mint KDE edition.
Is the KDE edition recently released compatible with the 64-bit edition of Helena and Gnome? Is there a way to download and install the KDE packages so on login I can choose which session I prefer?