I agree with http://kotaku.com/5800180/played-it-beat-it-still-dont-know-how-good-brink-is:
Should you buy Brink now? I'd wait. It's just now touching the oxygen of being played by gamers online. Let the chemical reactions take. Brink today is not the game Brink will be in a week; the game today may be better, it may be worse, but it's temporary. For now, I'll give you a shrug and tell you: I'm just not sure.
And I agree with http://arstechnica.com/gaming/news/2011/05/why-were-not-review-brink-and-why-you-shouldnt-buy-it-yet.ars:
My advice right now is to stay away from the game. The version of the game I played is a mess, and not worth your money. Keep an eye on the forums, check to see if reviews are updated as the game is patched, and then make a decision. Sadly, I'll be traveling starting on Wednesday, and the week after that I'll be out of the office taking part in E3 preview events filled with games I can't talk about. It's going to be a good long time before I can download the PC version of the game and tell you what I think.