I commute about 150 km / week on a Surly Cross Check SS. I'm currently running 39/16 which feels about right, I coast on steep descents but can keep up on flats and manage climbs. May drop to 14 as my shape improves. I've noticed that my commute is faster since I ditched gears, I think mostly because I'm faster uphill. It's also much harder though, but I see it as better workout :-)