I just got my papers from Progressive. Added on as a third car, the smart was $141 for 6 months. That's 50/100/50 coverage with 250 comp and 500 coll deductibles and a full-replacement value add-on. I live in Utah. I did another quote where I took off another car and the rate went to $194, so that reflects not getting the add-on car discount (though it's still a multi-car discount). For comparison, my '04 F-150 was about $250 and my '98 Audi A8 was about $300.
I'm very happy with the insurance price on this vehicle.