I'd second that: 4130 steel, with gusset, not flash - just a good solid stem. Good luck getting hold of one!
I'd also go for canti's every time. I remember reading an article by KB about how V-brakes were only invented because of cable routing problems on full-sussers and were just a gimmick on anything else... he also said (faily scathingly!) in the same article that no doubt disc brakes would become mainstream before long
Hmm, ask AgencyScum about that one - he had a brown-trouser moment because a single-bolt stem doesn't play nicely with a bar with too much rise / sweep