One cool new feature in Windows 7 that I think will be especially helpful for everyone and their Mom is the new file dialogue system. At first blush it looks like what you've used forever, but up in the right corner it has that nifty little "search documents" field. It instantly searches the titles and the content of your documents.
I'll say that again, in case you missed it. It instantly (as in right now, no waiting, or clicking, as you type) searches the titles and the content (if you can't remember what you called it, but you can only remember what you said) of your documents. This is huge. This is amazing. I love it!
If you're like me, you have files all over the place and sometimes it can be difficult to remember where it is. No worries anymore. I know that Mac has had their searchlight going for a while and the search feature from the Windows start menu is just as cool, but having that search feature there when you click "Open Document" is a perfect little touch that makes using Windows 7 a joy.