I have a friend who has about half a dozen TVMs now, rifles and fowlers, and he thinks very highly of them. I've had to do some little detail work on a couple of them, things that shouldn't have been wrong. TVM would have made them right but the expense and bother of shipping the gun back was just not worth it, not when he could con me into doing it for free.
I agree that I would not call TVM a "mass produced rifle". They will make anything you want, any wood, any lock, any barrel, any stock dimensions, left or right hand, carved, engraved or plain as dirt. I don't know how much more "custom" a firearm could be. They do build to certain standard patterns, such as Early Lancaster, Early Virginia, Southern Mountain, Leman etc but didn't all of the old time gunsmiths build to a certain recognizable style?