+1. This is a drop-bar bike. Hydro brifters are expensive. Like, 700bucks--and then you need to upgrade to Di2, as well.

OP: I like BB7s far more than BB5s, but probably not enough to pull off the brand new BB5s in favor of brand-new BB7s. I have far more experience with the long-pull avid disc brakes than I do with the short pull (I've never really worked on the road version), but I'm thinking that the benefit of dual pad adjustment might be slightly more important on the short-pull versions...

In any case, I'd go for the rim brake version, and see how ya like it. If braking performance is underwhelming, you could go with mini V's or a better cantilever set (Tektro Oryx aren't so nice... and that's not just Tektro snobbery. The cr720s have a very nice feel).... You'll still be saving money and headaches versus the disc version. Let's remember, Trek is marketing this thing as a "road bike for the real world". My road bike spends 90% or more of the time in the real world, and it has dual-pivot calipers.

hth,
Rob