Well, my trial and error and googling so far disclosed that simplymepis is using beryl for kde+3d so I went to the beryl sight for key bindings and mouse gestures. After reboot I was able to use the Ctrl+Alt+arrow combo to move between the desktops, open apps, etc. But then I noticed my kicker was empty on all desktops. So I started kicker (I then had 2, one blank, one with apps...blank one wouldn't respond to mouse so it wouldn't close). I was also able to vary transparency of a window with Alt-Scrollwheel, and *sometimes* after I move around among the windows with the scrollwheel on the desktop I can use the one I stop at...other times the desktop is just like a jpeg picture...clicking does nothing.
So, in summary: clearly this is very cool stuff, I like Mepis (so far) better than Suse so I think I'll stick with this distro on my spare machine for a while, and I suspect that the freeze-ups with KDE+3D may either be glitches in Beryl, or the integration with Mepis, or a subtle weakness of my old ATI AIW 7500 card (it would have to be subtle because all the other fancy cube rotation and transparency works great).
If anyone has anything to add for my and others who read this thread education please feel free.