Obviously it depends greatly on execution, but i'm not fond of the idea. I don't think it's a problem of the predator being able or willing to use our weapons or not, but more of a visual problem : it can humanize them too much. This image could stay in your brain for long, thinking of them behaving way too much like a human soldier.
That's not something we even control fully, but our minds are set to think of a predator in some ways, and mine is not ready to see a pred fire a human gun, even though i think he totally could.