Thanks to DWM (the compositor) in Vista, if you had decent enough graphics card, it was way faster than XP. Most of the UI issues were either that the GFX card was crap or the classic theme was enabled.
Vista was from a technical point of view, like going from MacOS9 to OSX...
They introduced a new kernel transaction manager, entirely new audio subsystem, new scheduler, new network stack, SxS, UAC, new display driver model, entirely new graphics stack, new power management stack, new crypto API, a whole load of new fonts and a proper stable 64-bit environment.
Vista was from a technical point of view, like going from MacOS9 to OSX...
They introduced a new kernel transaction manager, entirely new audio subsystem, new scheduler, new network stack, SxS, UAC, new display driver model, entirely new graphics stack, new power management stack, new crypto API, a whole load of new fonts and a proper stable 64-bit environment.