My PW has 'pink clouds' when ambient light is not strong enough. After 3 weeks of hoping the screen would either improve or that I would get used to it, I finally requested a replacement today. I used the 'Call Us' option on the support page to get to Kindle CS directly and only had to wait about a minute. The rep asked for a very detailed description of the problem, agreed that it was 'not the way it should be', and said that someone would inspect the replacement before sending it out. They are also pushing out the refund period in case I wind up sending both back.
I also reported a couple of software issues I've encountered (PW has failed to wake up 2 or 3 times—probably some resource leak—and the uneven text rendering problem). He seemed grateful to get this feedback and promised to report it to the developers. He also mentioned that an update was in the works, and they'd check to make sure the issues were addressed in it if at all possible.
It's going to be at a week before I'll know if the exchange results in a better PW (I'll be out of town when it arrives), but I'm cautiously optimistic. I'm glad I waited to do this, they seem to have a handle on things now. Not so optimistic that I'm ordering a cover for it yet