Hey there,
I've used them. It's kind of hit or miss... He does good work, definitely, but a lot of them don't match the originals very well. Apparently there was a problem using white ink, but then again, some of his sets DO have white ink, so I don't know what that's about. Maybe he started out not being able to use it, and now he can.
Sets that I particularly like and have used are the Snow Cat, the Flight Pod and the CLAW, all of which match the originals pretty well as far as I can tell. The VAMP looks to have a white GI Joe logo too, but I don't yet have one to apply them on. Most of the Cobra stuff is pretty good, but if you're looking to a HISS or a Moray, go with Ruben's stuff.
I prefer Ruben's stickers because of their accuracy, but the 334th stuff is good too, and seems to be getting better. I only wish he'd update some of his sets to match his better ones, in particular the Armadillo (since I have one that is in sore need of replacement decals right now!).
