Oh, I got one that went by almost unnoticed: Speeding up the sexp system by not using so many goddamn strcmps (Which I believe was kara's doing back before 3.6.12) Closing the event window suddenly no longer took 10 minutes
That was much later though. The change I am referring to was years earlier, and went by largely unnoticed (because the sexp system is rather fast to begin with).
It's kinda surprising that one was unnoticed. I detected an increase of around 5-10 FPS from it. The game was spending somewhere around 10% of the CPU time on that bug.
In the same vein though, Swifty's and Taylor's go faster stuff were very important too.
Closing the event window suddenly no longer took 10 minutes
Oh man.. that's one of my favorite additions... features?... fixes?
Funny thing about that one is that I never actually set out to fix it. I had built profiling builds for another reason and since I happened to have a FRED build I figured I might as well see what was causing that delay.
Even the way I solved it was pretty slapdash, I just opened a mission, closed the editor and hit the pause execution button. When I noticed that I was always in the same function, the problem was pretty clear.
EDIT : I split the threads. While I like the idea of a "What do you think the important changes are?" thread, I don't think it should be gumming up the 3.7 RC thread.