Well, right now I'm going Naked. It gave some chest protection, compared to nothing, but it really would depend on your size. I'm 6-1' and 215lbs. I've got a longish upper torso, so the wind caught me in the arm pits if sitting upright. If leaning forward it protected until the helmet.
If you were shorter and thin I think it would be better. I've got an M2 on order. Thought I'd try that.