I've been thinking long and hard about getting a 3D printer recently. After doing some research on the kind of things that can be constructed with the low-end devices, I've decided against doing it. The things which these devices can make aren't very useful, because the material properties are just not that good with regards to overall strength, temperature range, etc..
I'm now looking at my options for 2D printing, such as cutting parts out of plywood, acrylic, and such. However, the lower cost CNC machines have a very small work area.
I'd really like to get one of those position-correcting routers as in the recent MIT video, or something else which would allow me to easily work with a 4x8 foot plywood sheet.
Second the "build your own" CNC. A good friend recently made a 2x2 CNC that does a great job on wood and Halloween pumpkins for about $600. He did most of the structural pieces out of carbon fiber so it looks awesome but took some time. If you're building it yourself, it really doesn't cost that much to make a bigger one as structure and belts are not the expensive parts.