The linked artcile worked fine for me with vista, and I installed W7 with AHCI on and haven't had an issue. I'm not sure if anyone has switched it on afterwards though. Might be an issue to be addressed in W7 before release.
From what i've heard there's negligable difference in performance anyway, it's just for ncq etc iirc.
I installed W7 from a corsair voyager mini and the process was so quick and fast, so if it's really an issue you could just install again with it enabled in a similar way. That's assuming you're not using it as your main OS with progs on etc, which imo is not a good idea!