I actually have built myself one of these scanners - as a Christmas present for myself - and it works fine. As a student at the technical university in Norway I have access to a CNC router and could make the parts quite cheaply. With a hi-res camera, I can scan ~600dpi in color in about 4 seconds. It takes so long because I store the captured JPG-image and the raw-data directly from the camera, pluss I process the images in real-time instead of post-processing. If I only had taken the compressed jpg-image, it would have taken about a second (max two seconds) per dual-page.
Right now, I'm getting acceptable results. I have some problems with reflections in the glass, but that seems to be unavoidable with this design. I am experimenting with techniques for removing reflections and glare, but have not been 100% successful.
Rotating, descewing and OCRing can be done quite efficiently as post-processing by quite simple scripts. All in all, this is a very fine scanner for books. It can scan my old, valuable books without destroying them, and I now can read them (i.e. the digital copies) in bed while the originals slumbers safely in my shelves.