Mary Jo Foley reports that Microsoft has completed work on Windows Vista Service Pack 2 (SP2), just in time to meet their April deadline:

Microsoft has released to manufacturing Service Pack 2 (SP2) for Windows Vista and Windows Server 2008 R2.

Microsoft officially announced it was done via a posting to the Windows Vista Team Blog. It's tough to say exactly when SP2 will be available for sanctioned download. Originally it was expected by the end of April (which still could happen if Microsoft posts the code to one of its download sites by tomorrow). But it also could slip into early May.

All Microsoft is saying is it will start pushing the final Vista SP2 bits to customers via Automatic Update over the next few months. Customers who aren’t ready for it can use Microsoft's service-pack blocking tool to postpone the delivery of the SP2 bits from Windows Update and WSUS.

Microsoft also noted in the same Vista Team Blog posting that, as of April 28, it has begun pushing Vista SP1 bits to users who previously had blocked it using the blocking tool.

Read the official announcement as well.