I assume your on about a DVD upscaler? If so yes they do work reasonably well but like all things if the source is poor the the upscaling will be poor, but would still be an improvement over the SD source.
We have a Toshiba XDE600 in the bedroom which performs extremely well as a DVD upscaler & DiVX decoder too.
Edit**
Just googled dvdo, so mis-understood your Q

My bad & I have no experience with these so ignore my comment