Admittedly, my biggest experience with this game was probably the PS2 version, which is similar but missing a few things from the PC port... but still, it features most of the changes, and I was honestly shocked by how much more fun I had with this version than on SNES! The movement feels amazing with arguably the best feeling wall jump in Mega Man X history, I love the sound effects... honestly, if a modern version of the PC port added the option to change to between the soundtracks at any time from the pause screen and fixed the load times, it'd easily be the definitive version of the game in my eyes.
Rather importantly, the old PC port of X3 is not to be confused with the version available in X Legacy Collection. That version is the SNES version, which has some notable differences. So... why bother with re-releasing the old, forgotten PC port of X3? Could always re-release the PS1 version or something after all. Well, to me, what's most special about it is the rebalanced difficulty curve it optionally adds.
Yes, that's right, the old PC version of X3 exclusively, not even the PS1 and PS2 version had this, actually optionally adds a new easy mode, which generally feels like a more fine-tuned experience than the original game. If you're the sort who found X3's early game rough or unfun on SNES and only really liked it once you got powerful later on, you're in luck! This may be the exact version for you, if GOG ever re-releases it.
I still have some hope to some day get to see the dream of the definitive official version of X3 like that... as a huge fan of Mega Man, it'd be a dream come true! Let's see if we can get this overlooked gem of a port the attention it deserves, y'all!