I've only used an in-house 3d printer for one real job, although I send out stuff to Shapeways etc now and again. That job was to print some mounting plates with some captured nuts behind some stainless plate for some switches to screw into. If you're a bit picky, like me, you won't like the accuracy or the finish much of home 3D printing. For the job I described where you wouldn't be able to see the parts and they didn't need much strength, it worked fine.

The 3D print bureaus produce much better finish and have better materials (not that I like Shapeways much btw). Small parts are best for bureaus as they usually charge by the cm^3. So I use them for little parts that need a somewhat OK finish and don't have to be particularly strong. If you only have one part that you need right now, you might get some quotes from 3D print services.