I got it a few days ago actually, together with the Pokedex 3D Pro, and I really love it, I mean, what's not to love about shooting beams at clouds and bring back items and Pokemon with their hidden ability into your save file? And the best part is that it's not just tapping the 3DS screen with your stylus, you actually get to shoot at stuff that seem scattered around your room, it's quite nifty. My boyfriend makes fun of me for running around the house shooting imaginary clouds, but that's okay, I can just point my console at him and pretend I'm shooting him in the head, hehe.
I already got Therian Tornadus, and I'm very close to unlocking Thundurus too. I don't have any gen 4 games, so I can't get those games' mascots, but I just discovered that there are special extensions that are unlocked by entering secret key combinations, and you can catch Beldum, Slowpoke and Hoothoot too.