The amazing part of Chapman's 105mph fastball is hearing hitters describe how different it is trying to hit it versus other pitchers' 95-100mph fastballs. You wouldn't think 5% faster would make a big difference, but it apparently does.
Because this was from 2005. :) While old(ish), I had a conversation with a coworker and dug it up. Seemed relevant to HN how things work.