More leftovers from Monday's Avacyn Restored spoiler extravaganza:
A neat little combat trick and it's nice to see WotC expanding the mechanic a little farther beyond it's little box. But I do wonder if it'll get a little confusing if multiple paired creatures are tagged over the course of a long game.
It's hard to say if this will be played outside of limited or not. If Soulbond blows up big after a future big reveal and if the current meta could support a heavy aggro deck that uses that unnamed card (in Standard or Block Constructed), but maybe? But I think for now we all can assume that this is just one of those cards that will be limited exclusive.