Maybe some of the following ideas will help those wanting to control iTunes in the background (I don't).
1. If you are running iTunes on a Mac (MacBook, MacBook Pro, Mac mini, or iMac) running Windows (via Boot Camp) then you can use the Apple Remote with iTunes (Boot Camp 1.2 drivers added support for the Remote). Therefore with initially iTunes in the background you can press the menu button on the Apple Remote to bring it to the front, and use the remote to control iTunes as normal. Furthermore, if you also have the Microsoft Media Center remote, you can still use the Media Center button to bring Media Center back to the front (pushing iTunes back in to the background) and then control Media Center.
2. The KeySpan Express Remote is a USB infra-red controller with both Mac and Windows software. I have not tried this on a PC but on the Mac, the software has a special iTunes mode to let you control iTunes in the background. Even if you don't use this special mode, it can still be configured have the equivalent of the Apple menu button to bring iTunes to the front and then let you control iTunes. See
http://www.keyspan.com/products/usb/urm17a/homepage.spml
Most of the time, I actually don't use iTunes to play music, but to merely act as a server. I use a Roku SoundBridge M2000 to play music (I have three of them around the house), and this can be used with a Mac or PC. There are also other similar devices available like the Sonos ZonePlayer or the SlimDevices SqueezeBox (or even possibly the Apple TV or XBox 360).
Note: If iTunes is already in the front then you can even use the Microsoft Media Center remote to control iTunes!!