Hello M Moussa,
How said Walid Elshazly be careful. Is possible after upgrade to Windows 7, when you try to start Step7 to receive message:
Your user rights do not include the use of Step7
And how Mike J (guy with opinion in Walid Elshazly' link) said - "This Windows may contain bugs...
My opinion is also the same. Don't trust so much to Microsoft. Each new release from them "is perfect, faster, without bugs...", and suddenly just after official release of the product, they prepare Hotfix 1,2... or even SPs...So keep current position a little bit more and let's hope that really this new Windows would be better.