AC2 adds alot of stuff. But im most excited for the fact that you can now swim, i died 5 times from water related drowning in AC today, trying to get flags, and it angered me.

What do you guys like best? The improved AI? Setting? Inventions?

More assassin less warrior.

and shoulder scarf.

 I don't know how much they're changing the combat system but if they added more counter-attack animations to that I'd be pretty happy. Interested to see what else we get to do with the dual wrist blades as well.

Argh, my quote button won't work.

Very nice, but the warrior thing is what let me slaughter my way out of failed assassinations

Better and more missions.  I loved the basic gameplay of the first all around, even the combat which a lot of people don't like, so better missions are my main draw to AC2.  The rest is just icing.  Sweet delicious icing.

More weapons (Duel Hidden Blades), better assassinations, and the game takes place in Italy.

This currency thing looks pretty awesome. Buying gadgets form DaVinci and upgrading your weapons seems awesome.

hopefully more variety. That killed the first AC

More variety= less suck  more awesome

Everything. Except from behind Ezio's costume doesn't look as cool as Altairs. From the front it's badass, but from behind less so. Also, his scarf needs more flow. That would make it extreme badass.

I think the notoriety system looks awesome, but all of it looks like a vast improvement, and the original AC was in my top 10 games.

Assassinate anywhere instead of a specific location.

more variety and the bad ass blade gun

just more kinds of missions and assassinations..... the first ac was still awesome as it is

I don't really know yet. I think from what I have seen so far the addition of flying and using the various fire pits around the town looks interesting. 

i really like the setting, the renaissance is a perfect time period for a game like this.

I haven't played it yet?

I absolutely love the new setting for the game(I'm a big history nerd).  I also love the double hidden blades.  Being able to swim is also a big plus.  ^__^

Swimming and the larger two-handed weapons (correct me if im wrong but don't you drop the weapons if you sprint or something). I think the Da Vinci stuff is the going to turn out to be the end of the series.

Setting for me, loved how immersion the original was. Played it endlessly through a weekend and couldn't stop. Why I loved it so.  
 
Though I'm also super excited to see what's happened with Desmond. 

The Villa.  I was on the fence on AC2, but then I heard about The Villa Ezio gains later in the game.  Sold.