I have not yet tried clipless, and I know everyone says I don't know what I'm missing. Anyway...

At least get toe clips. I personally think that commuting with regular pedals and no toe clips is pretty dangerous. I finally got some after about the 4th time my sneakers slipped off the pedals trying to pull out from a stoplight in the rain with a truck on my tail. Embarassing and dangerous. Toe clips will keep your feet on the pedals in the rain and snow.

All that said, I'm probably going to start thinking about clipless. I'll probably go with some cheap mountain shoes to start with.