Game Informer's Mass Effect 3 Preview Summary

Over on the BioWare Social Network, forum member "didymos1120" has treated us to a "lawyer-friendly" summary of the new hands-on Mass Effect 3 preview that can be found in the latest issue of Game Informer magazine. Mars and Tuchanka are the primary locations that we learn about, so I'm going to go ahead and quote from the paragraphs devoted to the former:
Moving on, apparently Vega initially isn't too happy about just abandoning Earth. Also, before you've left the solar system, Hackett gets in touch and asks you to go to Mars. The research team studying the Prothean ruins (which if you'll recall, came up in the CDN) has gone silent, and they may have discovered something related to the Reapers. Once there, an incoming sandstorm threatens to cut off communications with the Normandy, and you run into Cerberus troops outside who are interested in the same info. Shortly thereafter, you run into Liara, who was apparently called in to consult. She tells you the info was about an anti-Reaper weapon that was never completed.

Then we get some details on combat there: in one encounter the Cerberus troops will run off and cut off your pursuit, forcing you to go around. Cover is more appropriate to the location: couches, overturned tables, etc. There's a running battle on a tram system, and you have to abandon your own at some point and jump on the Cerberus one. After that part, we get introduced to the shield-carrying Guardians. If you manage to shoot and kill one through the little vision-slit in the shield, you unlock the "Mail Slot" achievement/trophy.

At the end of the mission, you learn there's a reason they've been keeping the Cerberus troops covered up in promo material: apparently, husk-tech has been adapted by Cerberus and used on its soldiers, resulting in glowing eyes and disfigured faces. The writer had Kaidan alive, and notes that he reacts to this by asking if Shep knew anything about Cerberus doing stuff like this. I.e., complete trust is not yet there (please feel free to rage about this somewhere else).

You then get to chat with TIM via hologram, and he warns you to mind your own business. You can ask what he's up to and he'll say he's after "What I've always wanted." In this case, he's not looking for a way to simply destroy the Reapers, but to tame them for (what else) advancing the cause of human dominance. TIM also declares that Shep isn't needed anymore, and we catch a glimpse of someone else in the room with him. The writer asked Casey Hudson who this is, and didn't get an answer, but was told that Shepard was given "a clearer foil" in ME3. Kai Leng seems like the obvious candidate to me.

After that, you learn that Cerberus had one of its own on the research staff, a woman named Eva, and she's been using this time to grab the data and she starts transmitting it. There's a chase sequence and it turns out she's been cybernetically enhanced (and heavily so from the sound of it). You chase her and she makes it her shuttle, but Vega saves the day by smashing into it with some kind of vehicle (article doesn't specify). This has the side-effect of wrecking the comm gear she had on her. Unfortunately, it doesn't kill her, and she attacks Kaidan, nearly killing him. Shep takes her down for good, and it's off to the Citadel.