Until becoming a Mac user, I used Mandriva. It was Mandriva 2009 and KDE4 that pushed me away.
Mandriva 2010 is actually much better. KDE4 is a little better now, while in 2009 it was unusable. KDE3 is still much better.
I installed Mandriva 2010.0 in VMWare Fusion 3 on my iMac. Everything is working really well; the speed is as good as native really. The only problem has been that in the default installation the mouse speed changes between the Mac desktop and Linux one. Under Linux, the pointer would slow down; as the pointer leaves the VMWare window is snaps back to normal Mac speed.
The solution is to install the xorg mouse driver; yes, you need VMWare-Tools but this does not include direct support in xorg.
On Mandriva you need to:
sudo urpmi x11-driver-input-vmmouse
After installing, mouse speed remains the same across Mac and Linux.
