Quantum of Solace doesn't live up to Casino Royale. It can't. They really, really want it to, but no dice.
The plot and villains are crap. The movie is nothing more than an endless string of chase and fight scenes -- which are awesome, mind you -- but yeah, that's pretty much the extent of it.
That being said, it's still a good movie, and ranks right up there as far as Bond flicks go.