I bought one. Used it for about a week and then sent it back.
I also have an ArcadeVGA card. I'm using a 25" WG CGA monitor.
I thought the picture quality of the ArcadeVGA card was much much much much better then the Happ's UVC. Sorry, I don't have any pictures. The UVC is easier to configure and get working than the ArcadeVGA card but the UVC has kwirks of its own. Everytime you switch resolutions, the UVC switches to it's logo for a second or two, then switches to the new resolution. And sometimes it wouldn't switch to the new res, it would just sit there and display the logo like it couldn't sync and you had to switch back to the old res. If your not using one of the three resolutions, all your going to see is the logo. That means no display for people who use DOS. I think the picture quality looks bad compared to the ArcadeVGA card because the ArcadeVGA card can display many different resolutions including high res interlaced and the UVC only displays one resolution regardless of the input. I didn't even try using my Act Labs light gun with the UVC so I don't know if it will work. But the light gun does work with the ArcadeVGA card. So if you have a choice what to use on a CGA monitor, I would recomend the ArcadeVGA card.
Kevin
