I don't want or need a mod to charge my phone or anything else. That alone dismisses it for me.
As a general rule I'm not fond of "convergence devices"; often they end up being mediocre and not performing their primary function well. I don't want a flashlight (a la the Beyang 30w) or USB charging on my mods. I have Cree XM-L/XP-G flashlights and 15,000mah chargers for those functions. I'd rather that mod manufacturers spend their time and resources on making mods better than figuring out how to cram some half-baked nonrelated functionality into their products; to me it seems to cheapen a product a bit in the long run. I'm not saying that the MVP3 specifically will be cheap or won't work well as a USB charger, but I'd rather that Innokin put a dna board with step down in it than a built-in USB charging cable.