I have the Sony Touch Edition and love, love, love it! I can't say enough about it. I did tons of research before purchasing it and what sold me was the ability to buy from multiple sites and the borrowing from the library. Plus, being able to hold it and see it helped trmendously. I love the eink feature and prefer not to have the back light. I also like the Sony cover that has the light built into it.
Having shared that, the Nook would have been my second choice. They each have pros and cons about them. Good luck with your choice. You will love having all your books with you.