It depends on your needs they are not for everyone. Personally I find 3D printing to be very cool look at a site like http://www.shapeways.com/. All you need to do is submit a 3D drawing and you can get it print a few different types of materials. You can make cool custom art, jewelry, useful knick knacks, or fun gadgets. Home 3D prints are nice too but your limited to plastic and usually a smaller build profile. I could think of many uses for a home 3D printer but the cost is still to high.

As a commercial product they are even better, I recently persuaded my company to buy one. Now when we design cases and housing for customers we send them a 3D sample + the draws. In the past we would send only the drawings and if we wanted a sample made it would take 1 month + cost 500 times more then it does now. It helps our designers as well who now can instantly print out their work and make sure it looks good as a physical product compared to the 3D rendering.