Saw this last night, with a director and producer Q+A afterwards.
Monsters Inc is probably my favourite Pixar film, so this had a tough act to follow and I just about think that it pulled it off. It does get predictable in the middle, but once it finds its heart towards the end it's wonderful. Mike and Sully are great together again, but maybe Pixar underestimated how much Boo gave to the previous film, providing wonder and the foil against which Sully and Mike could react.
It was interesting to hear some of the answers in the Q+A too, including the decision to have Sully and Mike meet at university, which creates a couple of continuity errors with the first film. It was also good to hear how they wanted it to be a story of Mike's failure, and the identifiable (at least to me anyway) moment of heading from school, where you're top of the class, to univeristy, where you are average and can feel dwarfed by how well-connected and worldly everyone else is.