So, the general internet consensus is that this game did everything right that the first game did wrong and it's hard to argue with that statement. It's a beautifully polished game, and for the most part, the entire amount of time I was playing the game I was having fun. The feel of being an assassin is still very visceral, and by the end of the game, the array of ways at your disposal to destroy your enemies is staggering.
A few of the new weapons that you get in this game is having two hidden daggers, one on each arm, which at first seemed really silly, and it is, but there's no denying how awesome you feel when you walk between two guards and just put your hands out and stab each one in the neck. There's also the ability to kill an enemy while hanging from a ledge, you reach up, stab him, grab him, and yank him off. My favorite new ability though, is being able to fight barehanded, and steal your opponents weapon, then kill them with it. You're also able to poison one of your daggers, and poison an enemy, however, this always made me feel very awkward, because they thrash around quite a bit, so much so that I tended to avoid that method in preference of something swifter.
There are a couple of areas that I felt the first game was superior, one was that I actually liked having to do the pickpocket and eavesdropping missions in order to gather intel on your next target. Also I liked that if you saved a woman or priest from being harassed in an area, that they clergy would allow to hide amongst them, or the men would slow down pursuing enemies. In this game, you pretty much just do mission 1, then mission 2, and so on until you beat the game. The side missions are there just as an alternative way to earn cash, but really, if you cultivate the villa, money's never a problem.
Speaking of the villa. You have a villa now, that generates money every 20 minutes. You can spend money to renovate the villa, and open/upgrade shops, all of which increases the amount of money the villa generates. The shops also give you a discount over the standard prices. Additionally, armor and weapons go on display in a gallery, along with paintings you can purchase, all of which increases your revenue. Pretty much as soon as it was available, I dumped all of my earnings into the villa until it was maxed out, and then I never wanted for money again during the rest of the game.
Without getting into any spoilers, the story starts off pretty slowly, with Ezio, the character you are, just being a bankers son in Florence, with a slow buildup to being the Assassin extraordinaire. The resolution of the story was interesting, and didn't require that you had a constant vigilance for rooting out the tiniest details during periods of the game that you'd rahter not be playing. Also, Desmond in the present actually does stuff, and sets up a third game where maybe you would just play as him, instead of reliving the memories of his ancestors.
All in all, great game, lots of fun, highly recommended.