I've used this for a year now, and have had zero problems with it. The vent works great, the o-ring keeps the cap snug and leak proof (and my bike vibrates like a mofo). LC Fabrication makes great stuff. Fit and finish are amazing.
I put this cap on a smaller sized, custom built, prism style gas tank and it looks great. I would agree that it's a little small for most gas tanks though. It would be cool if a slightly larger cap was availible for gas tank applications. None the less, Great Part!