Although in general I like what MS has done with Windows 7 (it genuinely is the best Windows so far), there is one constant gripe I have with Windows Explorer, that is they've "unified" the keybinding for Backspace to work just like in IE. That is - instead of navigating up one level in the filesystem hierarchy, it goes back in the navigation history.
It is highly confusing, because you might not notice it for a while, if you've navigated to your desired destination by drilling down folder by folder and then pressing Backspace to get back to the parent folder.
Where it breaks down though is with the nice new addressbar acting like a double for a navigatable breadcrumbs (a pretty nice and useful feature in it's own right) and an address input widget, when you've navigated in any other direction than one level down the hierarchy, you start getting into the apparently weird navigation behavior.
I can\t count how many times I've pressed Backspace multiple times only to finally notice that I'm alternating between two folders.
This particular "feature" has pissed me off countless times since I had an impression that the ability to navigate up in the hierarhy via keyboard was simply gone.
Until today that is. I absently pressed a keybinding while in Windows explorer that I use constantly for this operation on my Mac and found out to my pleasant surprise that it did work exactly as I had expected.
The new Backspace replacement in Windows Explorer for navigating up in the folder hierarchy is Alt+Up