As per Microsoft, Dynamic Memory support and a more robust Remote Desktop client which uses RemoteFX are the 2 major additions coming via Service Pack 1. It will, of course, also include the various fixes which have been delivered via Windows Update prior to SP1’s release.
Download Windows 7 SP1
Warning: Downloading a major update to your OS from any source other than Microsoft itself is potentially dangerous and not recommended. More than anything else, I see hardly anything worthwhile included in the release worth the risk of getting a hand on the leaked source. If you are still desperate to try out this leaked build, here is the link Download Windows 7 SP1 {leaked} [via]Taranfx Update: Most of the links above have expired. You can instead download Windows 7 ISO here.