Disappointed... exchanged it
I took my recently-purchased 600 back to Waterstones. I was slightly nervous about this, since waterstones.com has a "We do not offer refunds or exchanges for ereader devices" disclaimer, but I thought I had a reasonable case of "Not fit for purpose." What use is a ereader if reading off it is uncomfortable?
Anyway, the manager of the store was polite and would have given me a refund, but instead I asked for an exchange, and took away for the smaller "Pocket" edition. This doesn't have the touch screen, and the screen quality is day to the 600's night. Brighter "white" level, and only point sources generate disruptive reflections in the pocket's screen, instead of any illuminated object.
Much happier now.