In talking to a number of people who've purchased or built a range of what I would characterize as hobby machines the common thread is that they are nearly unusable or a complete pain to use for real commercial work. Everyone I know who uses 3D printing for non-trivial business purposes either contracts out the work to 3D printing service bureaus with heavy duty commercial grade machines or they actually invest on such machines to do the printing in house.
That's not to say that hobby-grade machines are useless. The degree of interest these projects garner on sites like KS means something. Perhaps it means that people are clamoring for significantly cheaper solutions. Or, perhaps, it means they are happy to have 3D printers that perform reasonably well with some TLC.
At some level I equate it to what happens with CNC machining equipment. I've built and purchased many low cost home-brewed CNC machining solutions. In retrospect they were always a pain in the ass to use in one form or another. It was always far more time and cost effective to send parts out to have them machined by capable shops with capable industrial-grade machines.
I eventually purchased my own industrial-grade machines. I had Haas VMC's and a lathes in house. That's when I saw the light. The difference between the hobby/garage machines and what the pro's are using is massive. It went from screwing around with the machine to make it work, maintaing tolerances, deal with software issues, repairing it, etc. to just using it and producing very high quality parts every single time.
CNC machining, at that point, became a source of creativity that did not detract from the design process but almost added to it.
This drip 3D printing gizmo is great. Like I said, I am supporting it. I could be lots of fun. A professional tool it is not. Not at this stage anyway.