Many audio enthusiasts indeed do use software EQ because no headphone is 100% perfect. The problem most people run in-to when EQing is distortion, but that is because many people raise the sliders over 0dB. EQ should never be used to raise a frequency, rather it should be used to lower frequencies. My headphones, the Audio Technica Ad2000, have a hump at 4k, and while Musicbee allows me to fix this slightly, it also touches other frequencies near it which I don't want. Ideally a nice parametric EQ would be ideal, but I wouldn't mind a few more options.
Edit: Thanks for the plug-in though, I'll try it out.