"Clouds reflect sunlight back to space and therefore cool a planet's surface, and Grinspoon's preliminary calculations indicate that the effect can be dramatic - keeping the atmosphere 100 Kelvin cooler than without them.

Although more detailed modeling remains to be done, Grinspoon says the difference could mean that oceans and pleasant temperatures may have persisted on Venus for at least two billion years."

"More generally, if this analysis is right, it means that the "habitable zone" for planets around other stars may be much wider than has been assumed, since Venus had been thought to be far outside it.

Grinspoon presented his work at the American Astronomical Society's Division for Planetary Sciences meeting in Monterey, California on Saturday."
http://www.newscientist.com/news/news.jsp?id=ns99994136
Link from NASAWatch: http://nasawatch.com/

This relates nicely to an earier discussion I had with Mark Eby regarding global warming on Earth- in this discussion I brought up an extreme example like adding lots of water to Venus and this COULD significantly cool the planet, and also the fact that generally speaking, there are still a lot of unknowns in modeling global temperature.
Btw Venus temperature Mean surface temperature 482°C so instead 750 K it's 650 K- still pretty darn hot, but there would also be other factors which could lower it further. Looking forward to seeing the paper- maybe life on Earth came from the Godess of Love.