It's not an all or nothing system. I can glance at the gauges while looking at the road most of the time.
Early Saturday morning I was engaged in some, uh, spirited driving on a very quiet mountain road that also involved a new Boss302. Keeping the little Miata-engine above 5000rpm was key to keeping big Boss in sight. The tach is a very useful. I might not need it when just trolling along in stop and go traffic, but when working the car hard, it's essential.