The Sony Reader software that came with the reader has an option to export notes as an RTF file. I'm not sure whether or not you can import the notes into another device though.
I'm not able to find a user manual and I don't have the software on this laptop (I do on my other one, so perhaps I can find the information later). However, I did find a blog that gives a basic step-by-step of how to export the notes:
Export Notes and Highlights:
Plug the Reader into your computer with
the USB cable, open the Reader software if it doesn’t open
automatically, navigate to the book with the notes/highlights using
Sony’s Reader software, open it, and then click the green icon on the
lower left to export the notes as an RTF file.