Sorry, I couldn't hold myself to share with you the awesomeness that is Editor scripting.
I don't know if other engines provide such a tool, but the ability to hack every step in the importing process is incredibly powerful.
Just an example :
Basically, I have fighting characters, with precise data like frame time, hit power for each move, collision time, etc..
2 monthes ago, before I jumped into editor scripts, I had to enter myself all those datas in each fighter's class, and moreover enter manually all the split animations in the import settings... I got more than 60 anims per char .. A pain in the ass.
Cherry on the cake : I'm using mirrored models for right side fighters. So if I don't want to hit my overall FPS by 50% with a negative X scale, I'd had to mirror all the anims manually in my 3D too, and name them properly in unity import settings... 120 x 8 x 3 forms to enter... Depressing.
To make it short : now with classes like ModelImport, all I have to do is drag n drop any FBX in the editor, and bam, job's done.
Datas are written to my classes, mirrors are generated automatically by a script, and anim split by diggin a simple .txt file that I update each time I'm producing a new anim.
To an extent, we can imagine huge factorizing for some more complex applications, like automating avatar models creation from an external database.
I wrote this thread because according to forum threads, I can't see that Editor scripts are that much popular. They should, because they can save a truckload of time, which is vital on iPhone production