For your first commuter, you mostly want to make sure it's safe and reliable. After commuting for a year, you'll have a lot better idea what you really want/need.

My first commuter was a bike-shaped object from Target. It taught me 2 important things: 1- I can ride a 20 mile round trip and 2) riding the wrong bike can be painful and hard work. I bought my second bike on eBay and that taught me to be careful to pick a bike that's the right size. My last bike taught me to remember to lock the garage at night . You can learn a lot from your bikes.