Erythritol doesn't give most people gastro effects because the molecule is tiny and is excreted in urine. Never makes its way to the lower GI tract where it can be fermented and cause gas and stuff. It is a fairly good sweetener for cooking and such but it has a "minty" effect on the mouth. It isn't extremely sweet so mixing it with another sweetener is a good idea if you're cooking with it.

There's a good article on Wikipedia about sugar alcohol sweeteners.