True Sony readers have the best interface. But A touchscreen has nothing at all to do with saving you money.

As far as the library checkout function, it all depends on what kind of books you read and who published them. In my experience I have found that libraries don't have many books and don't carry the ones I want to read when they do, so no savings there for me. For you it might be a major savings.

As far as purchasing books, I find the Sony store consistently higher priced than Amazon or B&N. No savings there!

I own both a 350 and a K3. The K3 cost a lot less and on average the books cost less than the Sony books. I also find a lot more selection available for the Kindle. I love both readers and have both to cover all bases, but I totally disagree with your premise that a Sony reader will save me money. It didn't and doesn't.