I've been very anxious to play Brink for quite some time now. And I'm simply wondering if Brink will be compatible with Windows 7? And if so, is it going to be a STEAM game?

Yes. Yes.

I know that the game is also on Steam but I don't think it's a Steam only game? Aka you can still play it without Steam?

Considering it isn't only steam preorder that exists, yes.

I wouldn't count on it. A lot of retail games use Steam as a DRM method, which means you'll have to register it on Steam when you install and then keep Steam running if you want to play the game.

The fact that Brink has Steamworks only supports that ^