So, I was delusional and thought I could find a Paperwhite in my local Staples. They only had the silver K4 on display, reduced to $69. No word on the PW. When I asked about the new black one, the sales person asked the manager, who first played stupid and then very grudgingly got me a box from the back. They really are trying to get rid of old stock. Anyhow, before my brain kicked in, I found myself leaving Staples with a brand new kindle in my hands.
I can confirm that the font is noticeably darker, and, what's more, the background is now a nice cream versus the light grey of my silver K4. It is only a bit brighter, but the tint is so much more pleasing to the eye.
I loaded the same book on both NT kindles and did not find the new one faster. Also, the ghosting is noticeable on the new screen, probably due to the increased contrast, while it never was on my old one. I checked that the refresh settings were the same on both.
So, I am going to keep it. I would have returned it if it didn't have a better contrast and the really nice background tint - I almost wanted to not like it. Sigh.
Oh, and, yes, the black bezel does add to the nicer contrast perception, but I covered the bezels and the difference was still there. Text is more legible, colors more pleasant.