When using the round dial to manage our airspeed throughout the approach to land, for example, we are predominantly just glancing at the angle of the pointer. We don't care what the exact reading of the airspeed is, we are just checking for the pointer angle to be "about right".
FGD135 - excellent - spot on. On approach in the old Classic the airspeed would always be moving up and down around the target speed i.e. +/- some 5 to 10 kts - everybody would ignore the variation .... i.e "it's about right" - the quickest of glances, as you say, at the angle (i.e. the looking in/out thing) would confirm it and that's really very useful as you come over the fence in bad weather - NOW - you've got the guy in the other seat calling "+2, +3, +1"
and then, horror of horrors, with a panic raised tone of voice, "-1" (jeez)
Personally, I'm only good for +/- 10 kt
