I just upgraded the cranks/BB a couple weeks ago and it made a huge difference. Eighthinch cranks + UN54 107mm BB. Stock cranks weren't horrible but i heard somewhere that the cranks/chainring combo doesn't stand up too well to the pressures of riding fixed, as it was made more with the freewheel in mind. Plus I just needed an excuse to buy new cranks and step my gear up; jumping from 42/17 to 46/17 cut my 10 mile commute by about 10-15 minutes, which fits perfectly with the recently implemented lateness policy at work.

@badonis - thanks! scored that poster at a record store i used to manage. Still looking for a MHTRTC one.