At least it is in my opinion. Took me several hours to end up with this. Wish there were examples like these of somewhat matured formulas that detect several common issues with tags and filenames to choose from. Still would need to add some $replace functions to catch those slashes and whatnot, but generally this is the formula I am using now for my library. Can't be bothered to refine it further.
Why isn't there a thread like this in which users post their formulas? Or maybe google just failed to index. Anyway, it is there now.
Currently using this one. It's way less restrictive as the first one I posted.
%albumartist% - [(%year%) ][%album% - ][CD$left(%discnumber%,1) - ][$num(%track%,2) - ][$if($stricmp(%artist%,%albumartist%),,%artist% - )]%title%