Lots, but there is still lots to go.
Mapping wise, it's nearly complete. However, I keep finding new places to add as I come up with new quests that need specific locations. I am TRYING not to make it too big to start, so that it can be completed in stages.
Quest wise I have a few actually implemented. I have some puzzles implemented. I'm working on a second battle system at the moment, aside from the default. Yes, there will be the default battle system, but it will be designed to be minimal and "realistic."
Magic system is completely designed, however there is a little bit of programming needed, and I may design some unique battle animations as I'm still using the ones from Hero's Realm. I think they are the only un-removed portion of the original.
I don't want to give a % as it would be entirely guesswork. It is a ways from release though. If by chance you can think of any way to speed me up, please let me know.