I can place a "cue sheet" on my handlebars in any of half a dozen different ways. Clips, clear plastic holders, you name it.
I do this as well; the problem is that by the time I've looked down at the cue sheet and located the next turn-instruction, my eyes have been off the road for 5-10 seconds. It's long enough that I don't feel safe doing it very often, which means I either ignore the cue sheet (and possibly end up taking a wrong turn) or pull over and stop every time I need to check the sheet (which is inconvenient -- doing it at red lights helps, but sometimes you need to make a decision at a place where you don't really want to stop).
Most everyone I know, including if not especially beginners, consult Google Maps and think carefully about their route because of safety concerns. By the time we're on our bike, we probably know where we're going and how to get there.
The above is true when I'm riding by myself to a familiar destination, but often I'm on a group ride where there is a set route, and if I want to stay on the route I need to know not just how to get to the destination, but which streets to use to get there. Typically the route has several dozen turns on it, so it's not something I'm going to easily memorize before the ride.
I could see this device being useful for me, although it would be best if it had a way to read the route sheet file automatically, since entering in the route instructions manually before every ride would be tedious.