For me personally, the grainy quality one might hear from the GR07 is basically them accurately reproducing every little bump and nook in the waveform, where as other smoother IEMs almost go over the audio with a sandpaper and minimizing the texture of the sound (which some prefer obviously).
Skies, if you have Terminator 2 available on your computer, play the minigun scene with the GR07 and the original tips. That scene was a bit of a revelation for me. When you've heard that scene with the GR07s, it's almost impossible to not hear how pretty much every other headphone just doesn't get to the same level of unrestrained, faithful reproduction of the snap, crack and kick of each gunshot throughout the register, and it's pretty amazing how tight and unsmeared it can get.
Love the GR07s for gunshots and action films.