They do look pretty good, especially considering that the light is at 24 in a dark room!
The difference really might be due to the font choice. For an actual comparison you should probably use the same page of one book with the exact same settings.
I though it could be interesting to take a picture of a Paperwhite, then remove all saturation and loop it in a gif, so that's what I did:
http://makeagif.com/i/jlpACa
The quality does suffer a bit due to resizing and the compression, but I think it's still an interesting comparison.
Also, regarding the original topic here, I should receive my replacement PW tomorrow or the day after that and I'll keep you updated. I've heard reports of other German customers actually getting older models than the ones they purchased (in terms of serial numbers and firm ware), so that probably wouldn't help much in establishing whether they've gotten better
But there seem to be pretty considerable differences in the color temperatures of different units.