kinda, they added in some extra side missions for the PC release that didn't make it to the PC version.
they probably had them planed for DLC, but then the game was such a horrendous PC failure that they decided to drop support for it in order to get Assassin's Creed 2 out faster, as a result the PC version got it for free as an enticement to actually buy the game instaid of pirate it.
What are you talking about? This is wrong. Every single copy of the PC version when released at retail was called "Assassin's Creed: Director's Cut" which had a few extra activities added in that the console versions did not. But there was no patch that added in things afterwards. And I thought the PC version sold well. If it hadn't there wouldn't be an Assassin's Creed 2 for the PC, you know?
To answer the OP, there are 1 or 2 new activities added in to the city when you go around investigating and I think they added in a fast travel option. If you own a PC version of this game, you already have the Director's Cut. If you own a console version and thought the game was just okay, you "might" want to give this a try. At the very least the story is great enough to warrant a playthrough.