If you've pre-ordered Brink on Steam you might want to fire up the service and hit the pre-load button on the game. The download weighs in over 5GB - so depending on your connection - it could take a while. Pre-loading gives you the ability to play the game as soon as its "officially" released, which by the countdown clock on Steam will be Tuesday, May 10th at 12:01 AM. Just fire up your steam client, click on Brink in your library and click pre-load.
I know there's a few staff members that pre-ordered the PC version and might just be playing on release night. Hope to see you there for the game's 8 player co-op!