Can't speak for everyone, but in every car I've ever driven, including speedos mounted in the center, if I'm checking my speed, my eyes dart to the reading and then back to the road. It's a fraction of a second, and I don't check speed very frequently. Every vid I've seen of the placement of the speed on the Model 3 seems to indicate I can do just as quick of a glance (with no head turn required) and have my eyes back on the road.