The 20D will fire it....but you'll get no TTL abilities, so you'll be working with manual or autoflash and setting the camera accordingly in M. You should be fine even if the trigger voltage is high as the 20D has very high voltage tolerence on the hotshoe and PC connector, I wouldn't use it on a 10D or 300D however.
My friend has it and it works perfectly fine, and as far as the TTL ordeal, just shot in manual, its a quick setup. I just bought my second vivitar 285hv and they are amazing, probably one of the better flashes under 100 bucks, I use them as slave flashes, they are workhorses.
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Setup: One camera, one lens, and one roll of film.