What most amazes me about Airplay is that you can't Airplay between iPads and iPhones.

At least two apps have come out to expose that capability, both making it into the official App Store and both being pulled some while later - with no stink made. Likely because they were doing some undocumented API calls. This all happened in 2010 and early 2011, so again, it blows me away that with iOS 5 we still don't have Airplay between iOS devices that are not the AppleTV. Or with Macs for that matter.