I'd like to know what the difference is going to be, and if it is significant. I mean, of course there will be different tiles, and weapons and creatures named after Gears of War, but will it play basically the same way? You know, party of 'adventurers' with a 'GM' running creatures, etc.
Well Gears is co-op according to the preview that's been released, so there'd be no "GM" player, only a "party" of heroes trying to get through a randomly generated map alive. You could probably kitbash a variant for a GM player if you wanted, though. FFG appears to be touting the AI as incredibly devious and "like there's a mastermind planning each move" but only time will tell how much of that is hype.
We don't really know much about the actual mechanics yet, but I don't think it will be the same engine as Doom and Descent. As far as whether or not the differences will be significant, well, that's sort of a subjective question. What I think of as significant might not be to you. Your definition of "playing basically the same way" as provided is fairly generic, to be frank. Except for the aforementioned GM bit, I don't see how it could fail to fit into this mould you've described. Tiles, weapons and creatures from the video game? Check. Party of "adventurers?" Check. Perhaps you could be a bit more specific about what you want or don't want? Keep in mind that we also don't know too much for sure right now anyway, so you might just have to keep your eyes peeled for future previews.
I expect that , mechanically speaking, it will have more in common with the D&D board games (Castle Ravenloft, Wrath of Arshie,) because it appears to be of the same randomly-generated, AI-enemies vein. Hopefully it will improve the weaknesses of those games and build upon the strengths, but again, we don't know a lot for sure right now.