I agree, this feature is huge! There is some notable latency in finding other iDevices; my first time using it, it took ~5-10 seconds to find the other person. The main use case I'm excited for is to share files from my iPhone (on a grandfathered unlimited data plan from ATT) to my wifi-only iPad. If there's a pdf I really want to see on a bigger screen, I have an easy way now to transfer it over. Compared to 3rd party file-sharing apps, the airdrop interface is much more integrated to the OS (since one of the big trade-offs with iOS is that there's no notion of a directory structure so 3rd party apps can't transfer a pdf into another 3rd party app). I also am not sure how it chooses the username to show. I wish I had more control over the username it chooses to use for airdrop.