No issues with Vista or Win7 here,both are excellent on stability plus I have all possible drivers,do remember its up to the manufacturuer to supply the drivers not Microsoft(unless its their product)for their product,its called customer support,Canon have been very good at this compared to say HP for example,when Vista x64 was first released Leadtek had drivers out for my Leadtek USB DTV within 4 weeks(well done Leadtek).
I remember in the early days Vista got blamed a lot for lack of drivers when it was not the OS fault,things have changed quite a bit now however still a few lazy companies out there dragging their heels for Win7 driver support etc...
My rule is simple, I stay with companies that give good driver support,if they don't then I go elsewhere.