The Mygica arrived and I've been using it for a few days now. The device gives a decent video image, considering that the video is coming from the composite analog output of the TiVo, then being transformed to RF and then RF to VGA.
It has a VGA input with PIP so it can display both the cable image and video card output at the same time. However, it noticeably degraded the VGA image coming from the computer, so I didn't want to use it that way. Perhaps it wouldn't degrade a monitor with lower resolution like 1366x768, but it wasn't good enough for the 1920x1080 monitor I'm using.
I also didn't like the thought of sacrificing one of the two monitors to it. Then I remembered I had an old 19-inch non-widescreen monitor stashed in the closet among some other junk, so I dug it out and made some space for it on my desk (it was kinda tough to get 3 monitors to fit) and use it exclusively for the Mygica. It has some dead pixels which were sometimes annoying it when using it with the computer, but are practically unnoticeable when using it to watch TV.