I've been using SizzlingKeys for the last couple years and I although I love how it lets me control iTunes, I *really* like how it lets me activate the screen saver or put the computer to sleep with just a single key press. I dislike having to use the mouse to do either of those tasks, and I do them both often. SizzlingKeys is a lifesaver.

I often have difficulty upgrading SizzlingKeys at work, because of the system configuration, but once I get it working, I'm happy with its responsiveness, configurability, and user interface.