You want some pretty sturdy tires and I don't know that I would go any lower than 32's. There's plenty of choices like Armadillos and Gatorskins. They can be pricey though. If you're good at changing flats quickly, it won't matter much.

They don't necessarily have to be slick, but a lot of tread is not necessary for sure if you're riding mostly pavement.

When the snow comes, then you'll need studs with some tread.

As a side note since we're talking various styles of bikes, I almost purchased a Trek Valencia electric assist. That would be really nice for long commutes. That sucker would bump you up to 20 mph in no time if you wanted it. Talk about heavy though.