After spending more than a year with Windows as my primary OS, while I miss Mac OS X I have to give credit where it's due and say that there are a select number of UI features on Windows that I like and wish would be implemented on OS X. This is a smaller one, but I do like the way Windows provides dynamically generated previews of folder contents in folders when browsing in icon view. It's similar and superior to the Dock's Stacks view of docked folders - I've never liked Stacks, but I do like the way folder previews are generated in Windows.
Now I did find something of a replacement for this feature in Snow Leopard, and I want to know if it still works in Lion. You can enable through a defaults write command the "Quick Look XRay Folders" feature, which turns folders viewed in QuickLook transparent so that you can see their contents. The previews are smaller than I'd like and still not quite as functional as what's in Windows 7, especially because instead of seeing them in the Finder window you have to QuickLook at the folder. Really it's not much of a time saver versus just opening the folder and looking at its contents, but I do like it.
Here's the command. You have to relaunch the Finder after you enable it: defaults write com.apple.finder QLEnableXRayFolders 1