I’m working on a detailed research note providing clients specific guidance on planning and deploying the 15 or so security features of Windows 7.
Two things you can do now to improve Windows security (regardless of your deployment timeframes for Windows 7):
1) Get off of IE6. I don’t care if you go to IE7, IE8, Firefox, Chrome, Opera, etc. Anything is better than IE6 from a security perspective. And this doesn’t require a move to Windows 7.
2) Continue to run more users as standard user. Ideally, all of them. It doesn’t take the User Account Control capabilities of Windows Vista or Windows 7 to enable this. Multiple third party products are available from BeyondTrust (acquired by Symark), Avecto and Viewfinity that enable elevation on exception (least privilege management).
I’ll post the link to the research as soon as it becomes available.