Being in Computer Science I am very confused with the NSF's system. Sending 2000 emails on any server would take a matter of minutes, and uploading review sheets will also take a minimal amount of time. In fact if they did it like most websites do, to the users the rating sheets should appear to be uploaded instantly. I don't get why their systems would have to be down for 6 hours to publish the results.
On another point they should really announce results like some of the conferences I have written for do. They give an exact date and time that emails will be sent out. Even if that date was April 15th it would be better than waiting for their mysterious date. :-) Waiting a few extra days would be less painful than never knowing when the results will be announced.