I've got a Broadcaster Elite 32 which I used together with a Sunrize16-audioboard. It has a long black breakout-box with Composite In/Out, Y/C In/Out as well as YUV In/Out. The board supports Linear TimeCode in/out, Composite sync out, key out, black burst in and a genlock input (for sync).
I don't think it reads RGB(+S) but I can't remember if there's a switch in software.
The software (Producer from Applied Magic) is quite OK. It works as a normal timeline-editor but at the same time you edit in the timeline you also produce an EDL (which can be imported/exported). So you can edit in both graphical as well as EDL-mode.
The quality is very good when running 2:1 compression BetaSP-material but it requires fast disks and a good SCSI-card (I use a Fastlane) and separate disks for audio and video. It has it's own filesystem which the disks must be formatted with.
The best companion for the Broadcaster Elite are the Soundstage-cards (16 or 20 bit), also from Applied Magic. But I think these are even more rare than the video card.
It works in 4 channels (2 stereo pairs) with a Sunrize 16-card but unfortunately you can't alter volume or panning from the Producer interface. This works in realtime with Soundstage-boards.
And it can't make transitions in realtime, everything must be rendered. There's PPC-modules for faster rendering (PowerUP).
Hope this helps :-)