If you’re a Windows 7 user then yesterday is the day you’ve been waiting for for a very long time – Windows 7 Service Pack 1 (SP1) is available to all. Previously it was only available to those with a TechNet or MSDN subscription. And also available is Windows Server 2008 R2 service pack 1.
Windows 7 and Windows Server 2008 R2 SP1 helps keep your PCs and servers on the latest support level. It also provides ongoing improvements to the Windows Operating System (OS), by including previous updates delivered over Windows Update as well as continuing incremental updates to the Windows 7 and Windows Server 2008 R2 platforms based on customer and partner feedback. This enables organizations to deploy a single set of updates.
Windows 7 and Windows Server 2008 R2 SP1 Features:
•Keep your PCs supported and up-to-date
•Get ongoing updates to the Windows 7 platform
•Easily deploy cumulative updates at a single time
•Meet your users’ demands for greater business mobility
•Provide a comprehensive set of virtualization innovations
•Provide an easier Service Pack deployment model for better IT efficiency
If you want to download entire thing it is about 2GB, but if you are going to update from your existing Windows 7 it is very low as 40MB to 88MB. Today when I try to update my Windows 7 Ultimate to SP1, it shows only 40MB.
You can find more information about this update Here