I have the easy angle and companion angle, and this is basically those two combined. I bought them for an earlier BH mystery, before the essential ruler was available.
I think I prefer having the two, as there aren't near as many lines and that gets me confused. However some times I grab the wrong one so at least that wouldn't happen with only one ruler. My companion angle ruler is quite a bit bigger, so I also use it for cutting larger diagonals.
I also love my Tri-Recs ruler set.