Re: Update to 190.42 breaks Xinerama AND TwinView!
Oh, and I should mention that the fact that your toolbar stretched all the way across your TwinView desktop is most likely a result of the "NoTwinViewXineramaInfo" option you have enabled in xorg.conf. The fact that you cannot rotate an individual monitor in TwinView is indeed a limitation.
As for the ability to switch desktops on the separate screens independently, that's not a limitation of TwinView itself, but the desktop environment. You should see the same limitation with Xinerama.