I originally got it just so I wouldn't need to switch in and out of map mode. As I started using Remote Tech and trying to put relay satellites in exact orbits however, I needed it for the orbital period statistics. I've just continued getting more use from it since then. I love the alt. above surface readout, the biome readout, the vertical speed readout, and it goes on. It's a great mod and I love the HUD Windows as they're not very intrusive and you can select what you want posted in them.
And you can't forget the delta-v readouts in the VAB/SPH.