FYI, we've installed 3 Compix systems, and there are at least 2 others around our city that I know of and they are well worth it. They are rock solid and easy to use, Windows based, import Targas with transparency (also imports formats like jpg, bmp), have a multi-channel option, external key, and more. We use one in our studio downstream of our VT4 for all of our CG and also in our truck. It scrolls beautifully. You have to buy the card and software together, or you can buy a turnkey computer.
The scrolls on the Amiga toaster were great and still hard to beat. We used them for over 10 years. Problem is, its not the highest resolution (try using small fonts), its monochromatic, no image scrolling, and only 5 speeds. In the Amiga VT you can't bring graphics in with effects (you can from switcher but then you can't change them on the fly) and you have to put the VT downstream which begs for the Guru Meditation message (or split off your cameras to it and never have matching colors). But that technology is still great stuff.