I've made a few tweaks recently. Since these changes, I shaved 10 minutes off my 14 mile (one-way) commute - and in essence, my avg MPH changed from about 10 to 14 MPH.
- Shimano M520 SPD Pedals
- Pearl Izumi X-Alp Seek Bike Shoes
- Ergon Performance Grip GC2
- Adjusted my stem 50 degrees forward
By adjusting the Ergon grips accordingly with my stem adjustment, it's still a very comfortable ride, but combined with the clip-less pedals/shoes, it turned out to be a very significant improvement.
Anyways, I'm a little anal retentive about shaving as much time off as I can from my commute and these few changes helped quite a bit.