But the bottom line from the Express team seems to be:

1. Mars had limited periods of time where liquid water was available in localized areas and produced clays during the Noachaian Era (more than 3.8 billion years ago, maybe only close to 4.5 G years ago). Hard to say exactly how extensive since the altered rock from that period they observe is rock that was covered up (but not obliterated) by lava flows or impact debris, but has now been exposed through erosion or other impacts.

2. Even shorter periods of time after the heavy bombardment (but not anytime recently) where highly acidic solutions produced sulfate evaporites in certain areas. Meridiani being a prime example.

3. Today, plenty of ice near the poles (in the layered deposits as well as the caps), but no sign of liquid water.

While it's not quite Nick's original "dessicated and frozen" vision, it does seem more like "occasionally damp and always cold" than like any sort of "wet and warm".