There were so many I've lost track. It runs fine and never crashes. It's highly playable, though a bit favoritistic to the human player. I did it because I couldn't stand the tech tree being so totally wrong. And because rubber wasn't that important for that long and because cannons were made out of bronze until the 1870s. Then I threw in a bunch of fancifull stuff I thought would be cool that threw the realism out the window again. Like the oracle doubling research.
To see the changes, you can look at them in the editor, or you can see the prerequisite structure and unit values in the civilopedia, like when you first learned the game. The only suprise should be the effects of wonders. Oh, and I also made barbarians archers--since why would they have horses where there aren't any--and caravels, so they can cross seas at least. And I reset the time to research advances to minimum minimum and maximum maximum.
However, for the highlights:
No new units, just all the unique units are available to all civs. These units are slightly modified--war elephant requires ivory, for example, samurai are slow, and legions can build roads (which I regret giving the human player, since the AI will not use them--this was done before I learned about telling the AI what to do with units. I should have given Legions full worker capability.)
All the wonders are really powerful, since the great ones all give you some kind of improvement in every city and the lesser ones all reduce corruption like forbidden palace. The oracle gives you doubled research capability, but you have to never get monotheism (now optional) or you lose it. To rebalance, play on a higher difficulty level.
Also, let me include here a justification: harbors could exist in inland cities because of river traffic.