I like the idea of iTunes controllers, but a lot of the apps I try are too CPU intensive or just plain feature-bloated, so I just live with some AppleScripts set to hotkeys. I discovered Bowtie a little while ago, though, and it's a perfect fit for my needs. It's tiny, unobtrusive and its look (and even functionality) is extremely customizable. It provides system-wide hotkeys for skip forward, skip back and play/pause. Depending on the theme you have loaded, the interface can provide cover art and song info, star rating controls and clickable buttons for basic playback control.
Bowtie has been out as a beta for a while, and I'm uncertain what its current development status is. I really haven't run into any show-stopping bugs, though, which is impressive for such an early beta. Of course, it's a fairly simple machine with a focus on doing a few things well and looking great in the process. What's not to love?