I am a huge Apple fan and I have been following a lot of things about the new Mac OS X and I understand the frustration raised by not having Airplay.
My Macbook Pro is a great computer and it works just fine and it is a lot better than many PCs that are out there and it will be for awhile. I am bummed about not having this as my computer is definitely not outdated (from a perspective obviously)
And people can easily miss out the fine print as they are getting excited about the larger font Airplay or the pictures etc and the feature itself.
People will voice their frustrations, this is why there are forums and support groups here. I don't see a reason to get defensive or rude about discussing thes.
Still a great update as an operating system and it is $19.99. Like everything else in life, it is not going to be perfect nor is going to satisfy everybody. However I was suprised that I was caught off-guard on this issue as I really rely on my computer to be a very good working computer.