I bought one, and she seems to use her possession quite a bit at lvl 17 ( and rising). It's funny watching her take control and go after something...the only time I switch her out is for the Lillend in parties, and that's for her group heal.
I bought 3 booster packs @ 300 zen, and got it in the 2nd one I opened. bull <font color="orange">HAMSTER</font> luck for the win. It has a great heal/crowd heal in parties. Not too often would I attempt a random box, having been burnt out in another game, but I needed the profession materials anyway.