I'm really, really upset right now...so I guess I'll just have to go with the facts. The facts about SIDS. SIDS has decreased 50% since 1983 (source - sids.org)(Since the Back to Sleep campaign started, IIRC). Belly sleeping your baby increases the risk of death 12.9 times (same source). SIDS.org has a chart that came from a study published in the March 2000 issue of Pediatrics, that says that infants cry more and wake more on their backs, however....they are equally likely to spit up on their backs and stomachs, and equally likely to choke on their backs or stomachs. Babies who sleep on their stomachs are more likely to overheat, rebreath their own carbon dioxide, and have more apnea (apnea is the cessation of breathing).
That is the research. It's not worth the risk. Take it for what it is.