Charging fine, backlighting not an issue IMO
Yes, the third generation Kindle will charge just fine from a standard USB port. Like the iPad or Galaxy Tab it probably charges a lot faster on a high-voltage USB port, but I run my Kindle for several weeks, then recharge it for a few hours (or overnight if charging from a non-mac laptop).
Unlike your experience with the Sony, it will run weeks without a recharge (assuming you aren't constantly listening to music through the surprisingly good (considering the thickness and purpose of the device) stereo speakers.
The contrast is quite good compared to the Sony, yes, and a notable improvement on the Gen 2 Kindle.
Respectfully, I think you're dead wrong on backlighting. Most of the time it's not needed; when it is, why not use front lighting which is much more natural for the eye? The $139 kindle has a $40 or so accessory -- a nice leather 'book' style cover with an integrated pop out LCD light powered off the Kindle's own internal battery.
I have used tablets for years (and currently have a Dell (don't like), Meego (beta) and Galaxy Tab. None of these touch the Kindle in terms of being easy on the eyes. (The Galaxy Tab is pretty similar technologically to the Gen1 Ipad -- higher pixel density, slightly lower resolution, and somewhat smaller display, but both IPS). I wouldn't spend 8-10 hours reading a Galaxy Tab/Ipad; I would and have done so with the Kindle.
Overall I agree with Bezos; I've been using tablets and PDAs for years; none of them touch the Kindle at what the Kindle is best at.
If you are a bibliophile, the 3G wifi Kindle is close to a no-brainer. If you don't spend 8+ hours a week reading books then it's probably not for you; you're better off with a good backlit device that does fantastic video (e.g. Tab, IPad).
[I have no connection with Amazon, Apple, Samsung, Google, Nokia or Intel. I do have a very tenuous connection with RIM [as someone affiliated with a partner company] who will be producing the QNX/Neutrino-based Playbook, but I deliberately offer no opinion on that device]