I used Synergy for a long time, and that was a fine app. SizzlingKeys is even better in terms of design and ease of use, has more features (the ability to search your iTunes library, locate individual tracks, and start playing them without ever leaving the application your working in is sheer genius), and decidedly more unobtrusive. Even if you pay for the pro version, you're still getting an incredible deal.

Since the developer invites feature requests, how about this: a hotkey to control the various Equalizer settings. Is that doable?