Is there some way to enable desktop composition with the Windows Standard colour scheme? I don't like the appearance of Aero Glass (which my card is more than capable of using), but I find that without it there's much more flicker and redrawing in general seems to be slower than with XP.
I tried enabling Aero Glass and then stopping the Themes service, and this seemed to work for a while (mostly - Window borders were still Aero themed, but I'm willing to live with that), but then suddenly Windows just disabled desktop composition.

The problem is, desktop composition is a part of the desktop window management (dwm) "Aero" features. If you do not enable the Vista Aero theme, you don't get desktop compositing because dwm isn't loaded/running. You can do what you did and just disable the Themes service, but this will only work temporarily - once a change comes along that would impact dwm, or a reboot or logoff event, dwm gets unloaded and compositing stops working.