I enjoyed the movie immensely. It went along at a good pace with a nice balance of exposition and action sequences. Knowing it was an immediate sequel to Casino Royale, I watched it a few days before. But anyone who hadn't seen the previous movie probably wouldn't have gotten as much out of Quantum.
What they should do in say, the Blu-ray release of the film (or on a separate DVD), is make a completely separate edit so that the beginning of Quantum flows directly on from the end of Casino - no opening or ending credits - and essentially melding both movies into a 4+ hour epic.