DirectX 11 what does it mean for us?
Well if you want all the new features then yes. Windows 7 Currently has DX11 built in to it, the new ATI and nVidia cards will support it that should be released around windows 7's launch.
Although talk that game developers are already working on numerous DX11 games, (will try and find a reference for that when i can), however i'm sure they will still work on DX11/DX9.
See
http://en.wikipedia.org/wiki/Direct3D#Direct3D_11 for some more info
Only real world test will show what improvements it brings.
act according to
http://en.wikipedia.org/wiki/DirectX#History, it could be launched (officially) very soon.
DirectX 11 6.01.7100.0000 Windows Vista, Windows 7 July 22, 2009 (Scheduled)