One reason to really like Tony Stark, Ant Man? He's an alcoholic with a killer case of the usual Stark-brand self-loathing. The fact that he could temporarily wield Mjolnir "freaks" him out because he doesn't believe he's worthy of the honor in the first place. Ah, yes: that's the good stuff! And it's more quintessentially Tony than, say, a Cosmic Iron Man who declares himself one of the world's preeminent minds. (Ahem. Not that I have a grudge against another Iron Man writer who shall be left unnamed or anything...)