I've had the pleasure of using both the xbox and PS2 versions of these, and I think they are both trash. The video signal has a lot of background noise and looks pretty weak overall. If you want the controls to work, be prepared to rewire your entire cabinet. The pinout is retarted. It uses the bottom 4 ground pins as buttons, as well as some of the other unused pins.
I would rather use ultimarc's adapters, as they use their hi-quality video amps. I made my own dreamcast to jamma adapter using ultimarc's dreamcast to arcade monitor adapter and a couple of stock dreamcast controllers. Picture quality is awesome on these.