Jethro, i bought my first roadie machine when i lived in atlanta, which is a hilly town. it had a triple crank, the middle ring was a 40T and the largest cog had 25 or 26 teeth, iirc. i pretty much kept it in the middle ring everywhere in town, starting from a stop on the 40T was not problematic at all. i imagine you'll be fine on the 39.

my commuter machine has mechanical disc brakes. i think a different model from the Motobecane posted, but still Avid. the bike is only ~8 months old and i have a short commute, so low mileage, but they have been problem-free. i haven't had to make any adjustments whatsoever. they take some getting used to, as the lever feel is different from rim brakes (pulls more cable). but they work just fine.