"Despite it looking like a short period of time between the release of Windows Vista and the first Service Pack, it is actually longer than the amount of time that it took for Windows 2000 and XP to have their first Service Pack releases.

Download size and hard drive space requirements have also been hinted at, with around 50MB required for the initial download via WSUS, with up to 7 GB of hard drive space required for the SP 1 install (it seems that the standalone image is going to be around 1 GB). Unless Microsoft have invented a new, ultra-efficient compression algorithm for the download option, it is probably going to be most efficient for most users to obtain their Service Pack updates on optical media."

Article Link: http://www.beskerming.com/commentary/2007/08/30/262/Windows_Vista_SP_1_Slips_to_2008
Microsoft Link http://www.microsoft.com/presspass/features/2007/aug07/08-29vistasp1beta.mspx