However, as I wanted to try and play Homeworld 2 on Vista today I upgraded my ATI drivers to 7.3 and now the game is no longer a flickery mess (huzzah!) however it still has issues which render it unplayable (boo! [sad]). However, this is progress and as such my 'Parallax' 'demo' now runs on Vista without being the aforementioned flickery mess. If ATI could just see fit to get the PBO extension back in the drivers for 7.4 then their Vista drivers will be better than the XP ones!
Also, no more uninstall-reboot-install-reboot for upgrading video drivers; on a whimm I just ran the 7.3 installer, selected 'update' and it appears to have worked fine (OGL working better for example).. still had to reboot to make the CCC work properly, however as that's like the first time in months I've needed to touch it I'm not too fussed about that (be nice if they fixed it however as it refuses to run until you reboot).
So, on the practical side, this now means that, aside from the full GPGPU method, I can work on my FYP's final stages in Vista and if by some chance April's drivers come with PBOs then I'll be able to test the whole thing in Vista and can wave bye-bye to XP x64.. huzzah!
Right, back to puzzling about what's causing the semi-numbness in 3 fingers on each hand...