When using an imperative form, what effect does the speaker's choice of aspect have?
More concretely — what's the difference between (for example) снимай пальто and сними пальто? In both cases, the speaker intends for the action to be completed "immediately", so the choice of aspect (imperfective vs perfective) doesn't seem to have it's usual grammatical significance.
Is the choice of aspect mostly a matter of "etiquette"? It may be just me, but the imperfective form (снимай) seems more polite. But I think I've heard plenty of native speakers use imperfective forms when they intend to be rude (for example, there's a scene in "Brat" when our hero tells a hooligan on the bus to "bezhai").