Well, since Netflix is built in to the new ATVs, who cares if the iPad can use AirPlay with it? The other ones would certainly be desired.
The point is third party apps appear to work with AirPlay. That is huge. AppleTV just indirectly got apps that make use of the touch interface of your iOS device.
It opens up a world of possibilities. I love my hockey, and the NHL has been considering an iOS app. Now if they make one, I can use it to watch any NHL game on my TV.
Any TV network can come out with an app and price it as they see fit.
Once established, you'll have a bunch of apps on your iOS device that would essentially serve as interactive channels allowing you to watch what you want, when you want it, and only pay for what you want.
The best part of this is that the apps are not on the AppleTV, which actually increases the chances of TV apps since networks are under pressure from cable providers to not rip their revenue stream out from under them, but they have no quams with allowing people to use other devices outside of the living room to watch video content (like on iOS devices). It's basically a sneak attack on the living room. Once it's established, it will be harder to take away, and ultimately set top boxes will be allowed to have more functionality. Traditional cable is going to have to change to compete.
Of course this is bandwidth dependent. I see a future where internet costs (hopefully just) a little more (more bandwidth, higher consumption), cable is dead and you stream your TV content off the internet, on demand, from the sources you choose instead of whoever your local cable provider happens to be. AirPlay could be the thing to really get this going.