We have one on our 2000 GB with the Ford V-10. Works great, no problems, will basically tell you everything you need to know about what's going on with your engine, and more. We do not, however, use it as a trip computer, so I can't tell you if it works well or not in that category.
We put it in a couple of years ago because the factory instruments have no numerical readouts, i.e., the engine temp gauge reads C and H, the oil pressure L and H. I wanted something with real numbers. Also, the Scan Gage can be programmed to read tranny temps, oil temps, etc.
Recently, the engine temperature gauge went bad in Jan's Chevy Trailblazer. I had no desire to tear into the instrument panel to replace the thing, so I took the scan gauge from the Coach and put it in the Trailblazer. I set it to read engine temp, incoming air temp, RPM and MPH and it worked fine.