There were some problems with the CS3 Notes Tool -but the CS4 version removes some useful functionality. A client will often return an annotated low res copy of a file -with notes indicating desired changes, revises, etc. It was often useful to have the annotated version open beside the current working version. The notes would be visible on the annotated file, as a guide for the working file. But with CS4, the notes are only visible in the notes palette -and they are not visible when the working file is active -unless the notes are copied to the working file -an unnecessary step. Why not allow access to notes both ways (with an option click?) It would often be useful to have multiple notes open & visible in a separate file.
An arrow tool in conjunction with notes could be helpful -to better indicate what elements the notes refer to. This would require a return to the CS3 notes interface -which I would welcome.
It would also be useful to have the option to designate colors to individual ruler guides. Multiple guides of the same color can be confusing.
The ability to convert drawn lines, rectangles, and other shapes into Guides would be more useful than just creating pixel layers as guides-which in error can be left visible & might print.