Hey va1n, nice you let us know! ^^ Good post!
Check the 'what changed' section for what is added to this version to keep stuff organized

IMHO Good strategy with constantly re-released SDK's is to d\l them all once in a year (for ex. january), and then stick with that to the next year (there won't be notable changes usually which force you to update more often), and as we know years run out of at some point, you max. need to do this 30-40 times and you are dead.
DX11 is starting to inhabit the SDK. Don't care though, it's not much different from DX10. So it should be safe to invest on 10.