good question. my own head is telling me that it'll act like gelatin and clarify the heck out of the wine, but that's only a guess. my only real knowledge of them both is to thicken sauces and that xantham gum is quite potent. guar gum is a bean derived substance and xantham is made from sugars. i don't think they'll hurt anything, right? I can definitely see them affecting body or mouthfeel though.
I'm interested to hear from experienced people on this one.
Primary: Highway 35 Scotch Ale (Highway 78 clone), second runnings small beer
Bottled: Pitch Black Sheep IPA, Juniper Fail/Ale
Kegged: Apollo Pale Ale, South River Brown