Having played around with it quite a bit, I've grown to dislike the hammer in the extreme. It appears to offer no tangible advantage over the sword (other than a small boost in range), and its drawbacks are extreme: it offers no protection from any attacks, its attack animation is much slower than the sword's, and, worst of all, half the time you hit an enemy with it, all it does is push said enemy around a bit.
It's entirely possible my experience is incorrect; perhaps I'm misusing it. If there's some tactic that will reliably work with it (particularly against jetpack bots), I'd be greatly interested to know. What say you?