The SP1 release is important because it provides us with an opportunity to address customer feedback as well as the security, stability and performance of our 2010 wave of products. The release underscores our commitment to improving the quality of our software over time. We are grateful to those customers and partners who have taken time to provide us the feedback that makes our products and services better.
As stated in MSDN website :TechNet Blogs
Today SP1 is available from the Download center. The Downloads Table below provides links to the new packages for SP1. If you have installed all Office Automatic Updates, you will also see SP1 available as a manual download from Microsoft Update. After a 90 day grace period, SP1 will be offered as an automatic update through Microsoft Update. Customers using the Office Click-to-Run technology will have SP1 streamed to them beginning in July.
Installing Service Pack 1
Prior to installing Service Pack 1 you should carefully read the known issues and release notes at