Yep, I've used it in games before, (or, rather I've used something very similar). It worked really well! The diamonds I usually just black out in something like Photoshop and ignore, skipping over them in play.
Something I thought of, but have not tried yet is random encounters. Pick your starting town and in the diamonds around it, put the number "1". As they radiate out from your starting town, increase the number. When players move within each ring, roll a d20. If the roll is equal to or under the number of the current "ring", you get a random encounter. Something I've been keeping in my back pocket to try in a West Marches or Open Table game. Just a thought!