Just got this from Konami:
“The interest in the Metal Gear Online Premiere Beta is incredibly high, with an extremely large number of users downloading the software from the PlayStation Store today. The Konami ID servers may not be able to meet all the demand and Konami Digital Entertainment GmbH recommends users try the Game ID/Konami ID registration process over the following days. Do not worry if you do not complete the registration today, as the play time will not start until Monday 21st April, so everyone who wishes to join the MGO experience will be able to register the necessary Game ID and Konami ID in the next few days.”
Sounds as though everything could happen as planned on April 21 in Europe, at least. Fingers crossed.