I don't write scripts for Heroes, because I don't need to. I write scripts for Mortal Kombat. It runs slowly, of course... I wish I could find a program that doesn't slow things down! That would be worth its weight in gold!!!!
P.S.: Ideally, it would be like in StarCraft. After a battle, you just press SaveReplay and you don't have to worry about anything, but unfortunately, they missed that in Heroes :-(