I love it, buy I prefer the French pronouncation. I think it's very charming and handsome, and wonderfully simple for such an elegant name. I'd pair it with a long-ish, sophistocated name like GuyArmand, GuyEdmund, GuyVincent, GuyBenedict, or GuyFrederick, but that's just me.
I know a guy from Canada who was almost named Gui--pronounced the French way, GHEE--after a hockey player, supposedly. He ended up being named Steven, which is a very good thing because his ln started with a GHEE sound. :-/ Sounded like someone saying Gigi wrong and then the last part of his ln. :b