Word on the street is the API for developing transitions for PrP is a big PITA. I had a large German developer who made great transitions for FCP finally give up on PrP because it just took to much time to program.
Boris Red 5 is really one of the few good solutions out there now for sophisticated and customizable transitions.
Tom Daigon
PrP / After Effects Editor
http://www.hdshotsandcuts.com
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