There's two problems with the current crop of 3D printers. First, the printers are fiddly. It is possible to print out decent objects on a good printer (personally, I'm a fan of the Ultimaker). However, it requires tuning the printer and the software and maintaining them. It's a solution for tinkerers, not for Joe Average. Companies like MakerBot are deluding themselves when they think they've got a RepRap-class printer they can sell already assembled "for the masses". They still need too much maintenance.
Second, you can't just print anything and expect it to look good. If your object doesn't require support material (overhangs are all under a reasonable angle), and the slices don't contain more than one connected surface, then it will look beautiful on a decent printer. If you need support material though, then you have to deal with removing it, which is nontrivial. If you have more than one surface per slice, then you have to deal with stringing. That's not too bad if the surfaces are far apart (you can remove it easily), but it's difficult if they are close together. These are the limitations of plastic extrusion printers today, and you need to design models taking them into account.
On decent prints: http://www.flickr.com/photos/marcan42/8542507791/in/photostream/ . That's a gear, about 8cm across. You have to get up really close to be able to see those layers with the naked eye (they're 0.1mm tall). The roughness on the top and bottom surfaces is probably on the order of 50 microns. It is possible to go smaller on this printer.
On fiddling: http://www.flickr.com/photos/marcan42/8543920590/in/photostream/ . Left print is before tensioning belts, right print after. Of course, one of the cool aspects is that I was able to print the belt tensioners on the printer itself.
I'm very happy with my printer, but I would never recommend it to someone who isn't already a hardware hacker.