Assassin's Creed II has come so far, except also not-so-far...
For those that didn't play the first Assassin's Creed, here's a summary of what you did in the game: running, riding horse, sneaking into city, beating people up, EAGLE DIVE, racing, 'ooooh, flag!', assassination, running home. Rinse and repeat some nine times, and finish with the most Epically Subtle Genre Shift I've ever come across.
Looking back on the first game, it's clear to see that Assassin's Creed II has...not actually come all that far. When you get to the second major city, you quickly realise you'll still be doing the same thing time and time again (and also come to the realisation that all of the 'Beat Up' missions are women being cheated on...hmm...).
However.
Where the second game does improve is that it's not as obvious as it was. In fact with the arse-kicking new moves you have at your disposal and the variety of weapons you can accrue it's almost one of the joys of the game, providing nice diversions from the main plot.
Speaking of which, the plot is superbly executed and well-written. A nice blend of vague humour and macabre undertones hinting at something more sinister going on, the (richly accented) dialogue seems to pull you in and drag the story out only so far as it needs to be. Downside? There's two plots running in tandem, much as the first game, and occasionally the overlapping can cause some jarring clashes (such as the ending of Ezios main plot).
Generally the game allows you to put the abilities at your disposal to good use, albeit in whatever way the game programmers saw fit. Some missions you're required to stay hidden, some you have no choice but to be exposed. And this is, perhaps, the games only major flaw: for a game called Assassin's Creed that actively encourages you to remain hidden as much as possible, it's also a game that often pushes you into exposing yourself.
This flaw also ties into the 'Roof Archers Won't Let Me On The Roof, But They Let Theives Loiter Up There?' and the 'Guards Also Took A Level In Freerunning?' flaw.
But after a while it all just becomes another part of the game, and you'll probably stop noticing it. Until, that is, you find yourself being chased across the roofs by 14 guards. Then you'll find it annoying again.
The game is, overall, a very enjoyable game. The character development is positively astounding, the vistas are pretty, combining flowing climbing and jumping to traverse a city is amazing, and it never fails to feel good when you do manage to complete a mission by being sneaky. The end mission leaves much to be desired, with another Epically Subtle Genre Shift (except this time, not-so-subtle in many ways), but seeing as the rest of the game has been such a joy it almost feels like I should have expected it...