iOS 4.2 (or 4.2.1) was just released and for those of us who have been salivating over the promise being able to print from our iPads (and iPhones) were sorely disappointed that the AirPrint feature that was promised several months ago is basically worthless. Unless you happen to have recently purchased one of 8 HP printers that Apple supports in this release, you just can't print from your iOS device. Period.
As far as the AirPlay feature is concerned, this continues to be one of the most exciting innovations in quite some time. Unfortunately, the promise of this feature is not all there yet. For example, it's very exciting and nifty that you can stream videos from your iPhone and iPad to an Apple TV. This works brilliantly and seamlessly when you're play videos from your synchronized videos and photos from your Photos library on any iOS 4.2 device. Oddly enough though, videos that were recorded with an iPhone or iPod touch and site in the Photos library cannot be streamed to an Apple TV. Arguably, these would be the videos that you would be most interested in sharing with others shortly after just taking them.
Another oddity with the AirPlay feature in this release is that it doesn't work with 3rd-party applications. For example, you can't stream Pandora, Netflix, or YouTube. Hopefully, that these applications can be updated to support this feature, but it's unknown at this point whether Apple is going to allow this. I would love have the ability to stream music from Pandora to my Apple TV or one of the promised AirPlay-enabled speakers (such as the iHome iW1 AirPlay speaker).