Woah, where'd all you guys come from? haha

You *can* commute on a bike with steep geometry and 23c tires, I do, and so do alot of other people. But it's a trade off and you need to be sure of what you really want. The fact that my bike doesn't accept fenders is a tradeoff I've made for a bike that is more fun to ride. 23c tires make for a rougher ride, but feel more agile. It's not the most practical ride, but the tradeoffs are worth the enjoyment I get, not unlike someone commuting to work in a porsche.

So give it some thought, the more practical suggestions are certainly good ones (in Toronto at Urbane Cyclist they have the Masi Commuter which is similar to the alternatives mentioned here as well) but don't think it's totally impractical to ride a fun bike for transportation as well.