The rising action plateaus, a mini-climax occurs, and many are left complaining about a lack of "plot". Personally, I think some people should take some time reviewing the elements of plot. This story doesn't lack a plot, it is merely not the entire plot of a story on its own. Perhaps the end should have been a giant "TO BE CONTINUED..." to help all of the less than observant viewers grasp the reality that this film's plot is part of a larger storyline.
Overall I greatly enjoyed the pace and action of the film. Perhaps I'm just an adrenaline addict, but the breakneck speed of events in this film was a welcome change of pace from other action movies I've watched.
I also appreciated the more gritty and raw version of Bond. Casino Royale reshaped the image of Bond as a more human character with real emotions, even capable of love, and hate. Quantum of Solace built on this persona by showing Bond as being loyal to M, passionate about avenging his lost love, and capable of caring about someone who has suffered loss and is also driven by revenge.
The use of revenge as motivation for characters is highly overused, but something that everyone can relate to at the same time making it acceptable. Yet this isn't Bond's only motivation making him slightly more complex than we first suspect. He wants to catch the bad guys, protect M, uphold justice, and help a friend. Perhaps there is even more to him than this, but that is what I am recalling at this point.
I would say that Quantum of Solace had more to do with developing the new James Bond, and introducing a story arch that, hopefully, will be quite compelling. I am really hopeful for the next film, and very pleased with Quantum of Solace as I feel it delivered on what it was trying to deliver.
If you liked Quantum of Solace, then I would recommend watching The Bourne Ultimatum. (As well as the first and second films in the Bourne series, assuming you haven't seen them yet.)