task:
How common is it currently to have a 3D printer at home?
Not common at all. There are two main issues:
- Price (though this is falling very rapidly)
- Software
The second one is the kicker. The main problem is that most people can't easily use a 3D printer, with the current software that exists. To get the best use out of one, you need to have proficiency with some kind of CAD or vector art program, as well as an understanding of certain engineering fundamentals in order to create working designs. Even if you have these skills, there is still a lot of fiddling you have to do with the software (or more likely, multiple pieces of software) in order to actually print the design.
In short - the software is difficult to work with, and it isn't simple "plug-n-play". I doubt it ever will be. At best, you'll be able to download designs or print out "universal" parts (think of a 3D printer that prints "lego" or "plastic meccanno" components) that can then be assembled. For a lot of things, that might be enough; but it wouldn't be the cheapest option if you need more than a few of the components.
3D printers have their place as tools in the maker's arsenal, but they are still in their infancy (think 1980's desktop publishing). I have no doubt they'll come of age and be really useful someday (and much faster, hopefully) - but for now they are a tool for the dedicated few.
A couple more links for ya: