Just remember, you will never be the fastest person in the world, or the country, or the state, or perhaps even your city. Your commute is just yours and your challenge is yourself. That being said the motor is the most important thing. Don't worry about others passing you, just try and beat yourself from yesterday. Use a tracking software and try to beat yourself from last week, last month, last year. Some of my best workouts come in the winter trying to beat my mountain bike commutes from the last winter. Building fitness will help more than anything - a pro on a beater could whoop me on a road bike.

Trying to beat others is just an arms race. Go for it if you like but I wouldn't worry about it too much. Good luck, but more importantly, have fun!