Library access was one of the deciding factors for me in choosing a Sony. Since I read books multiple times over, I always prefer to read before buying, and since an ebook reader costs a hefty chunk of change I want to do as much reading in ebook form as I can! Most of my reading over the past year has been library books.
I do admit, the Kindle has become slightly more attractive to me over the years - mostly because I'm sick of mucking around with ADE and am too paranoid to strip DRM, and also because there are still a very few books that interest me that are only available for Kindle.
Library lending sounds great, though I wonder how many libraries will add books for Kindle in the near future, as it seems to me they're pretty slow to adopt new things, especially on their limited budgets. The concept of ad-supported Kindle also makes me a little nervous - I do wonder what else they might come up with, and I prefer any ads in my books to be at the back where I can easily ignore them.
If I had a lot more disposable income I'd keep multiple devices around, but since I don't, I think if I were to buy a new reader today I'd still go with Sony. I don't care about wifi, internet browsing, or music, I've always had great experiences with Sony products, and after having held various models in my hands I still like the Sony ones best.