Originally Posted by downtube

You can upgrade the front fork, however it will be difficult finding 20" suspension forks in the US. Thus far I have recieved much positive feedback on the rear shock, hence I would discourage an upgrade there.

I think your best perfomance upgrades would be
#1 wheels (for light weight)
#2 adjustable angle upper stem (for comfort)
#3 double sided clipless and platform pedals (by Shimano)
#4 Quality Lighting system for commuting (Planet Bike is my preference)

You can also try to upgrade the cranks, and BB.

I would leave the stock handlebar, bar ends, seatpost, saddle, shifters, brakes. I do not believe upgrading any of those will give the rider much of a performance advantage.

Thanks,
Yan