This shows you what relying on the Web will do- I only just realized that last week's Nature had the Mars Rovers on the cover. The two rovers have continued to churn out geological information from their respective areas, and their observations have definitely changed my guess about the possibility of microbial life there.
Some conclusions of the Nature articles are excerpted at Space.com The take-home for me is the geological diversity of Mars and possible ongoing geological activity. Where there's a heat source, especially underground, I think the possibility of liquid water and then chemotrophic life goes up. An important caveat to this line of thinking is the abundant evidence of just how dry the rest of Mars seems to be. I blogged a while ago about large deposits of olivine, which appparently had not seen water in 3 billion years, sitting around on the Martian surface.