And has been for some time. I did notice a few changes but didn't think about those much. Now, Windows Secrets writer Fred Langa has an article on MSE 2.0 with it's significant changes.
If you are running Microsoft Security Essentials, it's now version 2.0. Get it here:
Microsoft Security Essentials 2.0 runs on XP SP2 and SP3; Vista Gold, SP1 and SP2; and Windows 7. The only thing to watch out for is is you run the 32bit or 64 bit versions of Vista or Windows 7. You can check this by looking in Start > Computer > System Properties. Under System, you'll see System Type and the Operating System will tell you there.