This is NOT my experience. Slicks are rideable in light snow without ice like is quite common with a surprise snowfall during the day but it is tricky. With studded tires in a simliar situation I had no traction problems. This is with the Nashbar 700c studded tires. Last year I was swapping wheelsets based on predicted weather. I would put on the slicks if the weather looked good for atleast several days in the future but would put on the studs if the weather predicted better than 50% chance of snow. I didn't find it difficult to ride in light snow with slicks if necessary. Ofcourse my commute is nearly all on salted roads that are well plowed.
This year my two wheelsets have the same rim width so it should make the swap even easier.
Craig