I came to realize that asking the question of SONY vs Kindle is much like asking the question of Captain Kirk vs. Captain Picard. It seems everyone has a very strong opinion on each device. Hopefully I will be unbiased
I personally have the SONY, I received it as a gift this past Christmas, and am very happy with it. I take this device every. The size is great and the platform openness (i.e. USB/PDF/RTF), very unlike SONY, is also a great value for the techi that I am. However I don't think I would have enjoyed the device so much if it wasn't for libprs500 and pdf2lrf.
Of course my initial interest was in the Kindle for 3 reasons, the wireless device, the keyboard and most important the content.
I have found that Amazon carries more of the type of books I tend to read and seems to have priced them all at $9.99. Most of the books I tend to read range from $20-$60 which usually translates to a price of $9-$30 for the equivalent ebook.
Of course if most of the content you and your wife read are fiction then Sony/Amazon/finctionwise/diesel are pretty uncompetitive. At that point you might want to consider the SONY Reader.
[EDIT]
BTW you can get any of the SONY classics from feedbook, manybooks.net and Project Gunenberg(sp?). So I would not get a 2nd SONY Reader just for the sake of getting 100 more classics. Plus these sites have many more free classics than SONY