When you need to shift across 2 or 3 cogs at a time, any linear motion system, indexed or not, has a huge advantage over STI, RapidFire, etc. When you want to trim your front derailleur cage, any non-indexed front shifter has a huge advantage over any indexed system. STI's only real benefit is in single-cog shifts, although a rider familiar with his/her downtube shift system can probably execute the actual shift just as fast. I have found barcons to be a bit slower shifting than downtube levers, presumably because of cable housing compression.