I'm going to be upgrading soon but no, you don't need a fancy bike to commute. You just need to be in good shape and have the right mind set. I bought a Marine (off brand) Kentfield from Sun & Ski sports a few years ago, it was around $400 on sale. I commute year round, 100+ miles a week. Buy cheap but invest is some nice cycling shoes, clipless pedals and cleats though, they make a huge difference.