Mass Effect 2 - CES Hands-on @ IGN

A 45-minute CES demo is the subject of a new Mass Effect 2 preview at IGN.  The article specifically describes this new mission they played in the press demo, so it may be considered slightly spoilery:

The mission takes place in the depths of darkness -- well beyond the Terminus sector and out of grasp of Alliance control. A giant space station, the Omega, has fallen victim to a deadly plague that's killing off the population at a rapid pace. It's up to you to infiltrate the enormous structure, track down a scientist rumored to have developed a cure, and ultimately save the day.

The scientist is professor Mordin Solis, a Salarian whose moral compass swings all over the place. He's a relatively good guy, but he's driven by results and sometimes the consequences of his actions -- even killing, if necessary -- run distant second to his primary goal, which is, of course, the cure.