Most of the code hasn't changed, however I got rid of the ZDoom style actor scripts, I've always hated them. Now each actor has it's own source file and is hard-coded. They take longer to make, but it's a lot cleaner.
I'm also thinking of changing the style from futuristic to Medieval. Maybe I've been playing too much Mageslayer, but I think it's better then trying to turn a first person game to top-down.