Well,
I have to say I was thinking kind of the same as your friend, insofaras to say what would make you stand out from a marketing point of view? The groups are a nice idea, but what I htink you bring to the table moer than anything else is your expertise from a programmers side. I think what would really make you unique is if you could essentially have two websites in one. Kinda like frosted mini wheats. Have your side that caters to the gamers and have your side that caters to the creators. The creators would have a dedicated group of people interested in playing the latest greatest releases and your devs would have the ability to interact and get immediate feedback on games they are working on. Eventually you could move on to having active blogs from different  contributors and more interviews with devs, especially since they would be coming through your site on their way up.

As far as operating systems, keep them seperate. Nothing irks me more than findin an awesome game I can't play. There really aren't enouhg native Mac/Linux games out there to warrant anyhting more than a section based on those operating systems, sad though it may be.

Question why will the comment box allow me to expand the box farther than I can see? That's just silly LOL. Well those are my bits of input.  Captcha rosebush evening...sounds like a feminine product