I also think the Three Caballeros El Rio was a slight step downward. While it was fun to see the Three and on paper it probably sounded like a good fit, somehow the story doesn't quite mesh with what was already there. Also, it would have been nice if the finale featured the three as audio animatronics instead of just statues as well as a bit more in the background (later I read they ran out of money).
On a more positive note, I liked the changes to the Haunted Mansion, especially the Escher staircases and footprints (the new interactive queue and the mirror effects at the end were still under construction when I went so I missed those). If I think about it too much, the idea of the stairs were probably a bit out of place within the ride context, but at least aesthetically the Imagineers did a great job blending it between the scenes.