I've seen it unpractical for me. I can machine one, I have all neccesary equipment, but it's unpractical.
Mind if you can tell why?
I know some people who has one since december 2012, pretty much the only device they use daily and they have quite a few other devices. I'm going to be the 4th one who owns one at our vape meeting. No complaint from them and I don't see anything wrong with it.