In fact I have barely ever tried them. I once made the mistake of buying a bottle of Tommy Girl as a gift and when tested (luckily before given to the girl), it turned out to be a really nasty fake. Nothing like the real stuff, but the packaging was really well copied.
I don't ever buy fakes, not in fashion, not in fragrances. Mainly because I think that the original stuff should be supported, it comes in nice bottles, it's decent juice, you know there's no health risk when used, etc.