I have played this game on XBOX360 and it was very good, improving on all aspects of the first game, including but not limited to; the graphics, mission variety, customization, and graphics.
However, for the PC version of this game, Ubisoft has implemented some measures to decrease piracy. So now, you need to be constantly connected to the internet to play, if your connection is lost, then you shall be reverted back to your last checkpoint.