Go see it. Simple as that.
It has action, great humour, the attention to detail for a period piece of this scale is fantastic, the chemistry between Downey Jnr and Law is more solid than the first and the cinematography is outstanding.
Sure it has some faults, a major villian just seems to vanish with no conclusion to his story and slow motion sequences are used a little too much, but for the most this is Indiana Jones in a top hat and tails or James Bond in a flat cap and tweed suit. In a year crowded with poor sequels and downright bad movies Sherlock Holmes 2: Game Of Shadows thankfully delivers the goods.
Sea State: Spray/Foam