Water behaves very strangely on Mars. <a href="http://www2.cnrs.fr/en/2753.htm" rel="nofollow">http://www2.cnrs.fr/en/2753.htm</a> -- Note the videos.
There are places on Mars where water ice is available year-round, and carbon dioxide ice seasonally, at high latitudes. Therefore, I'd say this discovery, at low latitudes, has few implications for colonization unless there's a fair bit of carbon dioxide ice mixed in. So I'm waiting for word on that before getting too excited.