It's a small thing, but my favorite Vista feature has ended up to be the ability to launch applications from the Quick Launch bar using the keyboard.

If you aren't familiar with this feature, holding down the Windows key and pressing a number will launch the application in the Quick Launch bar in that ordinal position.

For example, in the screenshot above, holding down the Windows key and pressing 3 will launch IE 7. (Pressing Windows-1 will launch Firefox.)

I find that I only use a handful of applications that I commonly launch directly, and this is a great way to launch them. (For example, I rarely launch Microsoft Word directly—I usually open a Word document.) I expected to use the new auto-search feature of the Vista Start menu to launch apps, but this is much easier and faster. I still fall back to the Start menu when I launch a rarely-used application.