PSN maintenance is scheduled to take place today, 26th April 2012, from 16:00 until 23:00 BST. Unlike other downtime periods, this maintenance will not cause any disruption to game play however it is possible that there may be intermittent effects on a small number of users.
So it’s not bad as the usual downtime. You should still be able to sign in and play your games but if there’s a problem, you’ll know why.