Frankly, I don't like this feature for two reasons.
I mostly play for Pokédex completion and never battle online. The only use I have for AR is to trigger events in games from previous generations (and only in those, I'll wait until X and Y release to start doing it in Black & White) , so I could get event-exclusive mons and no longer have to look at empty spaces in my supposedly "complete" Pokédex. Granted, in theory, for most event Pokémon I used AR to come across in Gen 4, the code is responsible for making items appear, which then lead to encounters with Pokémon that are generated by the games themselves, but they still might find a way to detect that it's not legit (I'm paranoid about the capture date of each Pokémon now being registered) . On the other hand, if they do tons of Wi-Fi events (emphasis on Wi-Fi) that will allow me to regain all the event Pokémon from gens 1 to 6, I'll be happy.
The second reason, and again, it's me being paranoid, is something I hated in the original concept of Xbox One: a key feature, which was working fine offline, now relies on a service on the internet. Granted, it's not as crucial to the game as in that case, the game is still playable offline, but the issue remains: if the service isn't profitable enough (which is unlikely, but in theory still possible) , the Pokémon Company might simply flip a switch and the compatibility between Gen 6 and the three previous generations will be lost for good.
A reason I might actually be happy about this service, and sign up is that, if I understand correctly, I will be able to create a "living Pokédex" (one of every species) and transfer it from game to game. After all the trading I had to do between my Gen 3 carts to get full Pokédexes in all five of them, I'll be happy not to have to do this anymore with a Pokédex almost twice as big.