As someone who has been trying to work through the Baulder's Gate series once more and trying to build a decent character to do so, I can't help but bash my head against the desk rather often at how unintuative and painful Thac0 is to work with and think on.
So a huge kudos to whoever came up with the seemingly far more obvious AC/AB/Save mechanic that was implemented starting in DnD 3.0.

PS: If anyone knows any Baulder's Gate mods that converts the displayed numbers into the DnD 3 version rather than the insanity the game came with, please please please let me know.