Pete Prodoehl of RasterWeb tells an interesting tale of his experience in making a replacement part using a home 3D printer. We've gone through this scenario ourselves, and you should hear this tale as it typifies the current state of affairs for home repair using 3D printers.
Pete required a light switch button and he wanted to try designing a replacement part from scratch, rather than simply downloading an existing model as so many 3D printer owners like to do. It's often difficult or impossible to find precisely what you need already designed for you.
The story unfolds with initial optimism, as Pete carefully measures the required dimensions and designed a simple replacement item in Google SketchUp. Pete's initial design concept seemed right, but it didn't print well. After several iterations and modifications he eventually landed on a design that printed adequately, as you can see in the image above.
Here's the lesson: some things can be quickly designed and printed if their geometry just happens to be compatible with the 3D printer in use. But it turns out that a great many objects aren't that way and iteration must take place, with each step gradually leading toward a geometry that is capable of being printed on the 3D printer in question.
Experiences such as this suggest the public could benefit immensely from a 3D printer that can handle more geometries than are currently possible with the current technologies used by inexpensive 3D printers.
Nevertheless, Pete got his switch.