One of my favorite and most-used iPhone apps is Apple's Remote app. It lets me remotely control iTunes, which is streaming to my living room stereo via an Airport Express. But why hasn't it been updated in over 8 months?
When the iPad came out, I was excited for what I assumed would be the inevitable update that would bring the app a similar interface as the iPad's iPod app. It would be perfectly suited for the device, with the big screen able to show more artwork and make flipping through a large music collection easier. It never happened.