Last night/this morning I put in basically a good 8 or 10 hours and just about finished florence before it was time to leave my friend's for work. I loved the first one but there were certainly plenty of things about it that I particularly disliked that I believe the second has made significant improvements on.
As an art history lover, it's great to see all these buildings i've learned about for years that are actually rendered in darn high detail, especially for a video game. The palazzo de medici for one really blew me away, complete with donatello's david in the courtyard, where it actually stood at the time (it's now kept at the bargello museum) as well as the medici crests and carvings above the arches. they really did their homework! sure accuracy only goes as far as it doesn't get in the way of game mechanics (i.e. the interior of the palace is likely far from accurate) but suffice it to say that I really love the setting and environments.
For gameplay specific changes, I really prefer the new infamy system, whereby ripping down posters, paying off heralds, or killing crooked officers reduces your wanted level, and it can be zeroed out. Compared to the tautological original system 'your warning level is your warning level' it is a vast improvement.
The villa, the architect, the bookkeeping, a good fast travel system, the fact that the collectables don't number in the thousands, the weapon and armor system, and friggin Leonardo DaVinci, seriously, I could expound on how much more I like this game than the original for quite a while, and I haven't even come out of the Animus after Florence yet. I haven't the slightest clue how the Matrix2-style 'Gee Willikers powers IRL? nowai!' thing plays out yet, but it HAS to be an improvement over the dreadfully sluggish and annoying 'real life' of the original.
Definitely looking forward to going back there and playing more of this, and if the improvements here hearken in any way to what 3 has to offer, I'm damn excited about that too. Really, I haven't been able to play any game for more than an hour or two before getting bored lately and this really scratched an itch.