While everything is improved,its still suffers from a few problems..... (possible spoilers)
AC2 starts off where the first one ended,Desmond,still stuck in Abstergo,gets rescued by Lucy and taken to a safe location. From there on they use a modified animus to delve back into the past,this time into the late 15th century. You play as Ezio Auditore Di Ferenze *takes time to catch breath* an Assassin. I'm not going further though,I already revealed probably too much. (sorry!)
Fortunately,the mind numbing repetition is gone this time. You now have tons of things to do,from buying weapons and armor to renovating a town,there's also hundreds of collectibles to collect. There is also a moderate variety of side missions that range from assassination contracts to beating up a person. You don't need to investigate anymore to continue the main story and you won't be jumping out of the animus after every memory sequence.
Besides the added stuff,the basics still stay the same. You can still freely traverse the rooftops and streets of the various cities in the game. The combat system is also more of the same,just improved.
The graphics for the game is good,that is,if your looking at the environment (which is amazing in size and detail). I wish the same could be said for the people,some of the characters faces lack detail. Otherwise,its good enough,could've been better.. The game also suffers from frame rate problems,especially when you open the map. The game even freezes when you do a certain action too much,but fortunately,its not a common occurrence.
The wanted system was also renovated,you can now be notorious permanently until you do things to remove it. These things range from ripping off posters (which,for some reason,are on top of buildings),bribing heralds and killing officials. The system works well.
In a nutshell: AC2 is a major improvement over its predecessor and definitely worth a try. Its got beautiful environments,a great story and the amount of things to do will also keep you busy for easily 15+ hours.