In short, I like it a lot when I remember to use it (which is spotty, but getting more frequent). I have it set to show on Win-Q (the default) at the location of my mouse cursor (not default). You can run commands there as if it was the command window or Start->Run, but you can also create “MagicWords” to be shortcuts to other programs (with or without parameters). For example, if I type Win-Q then “mor” (for morning), my e-mail, my RSS reader, and iTunes all open.
The best thing about it: it’s free! 🙂 Long live the keyboard!