I guess I'm just not an educated vodka drinker. In a mixed drink (which is how I drink vodka on the occasions I do have it), I can't tell the difference.

On hand I have a 1l bottle of Grey Goose I picked up cheap at Duty Free, and Crystal Head vodka, a Canadian vodka that comes in a nifty crystal skull shaped bottle - I bought that one for the fantastic bottle and the furor it caused when the LCBO yanked it from the shelves.