[j.p.s]

Originally Posted by tomsem

One difference is that the K4 supports Invert Black and White and K3 does not. Another is that K4 has Power Save feature, no other Kindle has this (yet).

I'm pretty sure that the Oasis 2 does as well. It just doesn't have the option to turn it off

Does the PW4 display "Waking Uup" for a few seconds when it is turned on after being asleep for over 30 minutes? (Are you intentionally using K4 to refer to what most people here call PW4?)

Originally Posted by tomsem

Normally they back port features when the hardware supports it, so I infer that these features are built in to the CPU or some other chip that has shown up.

If the Power Save feature is hibernation, that might not have required new hardware, although new hardware might make it more reliable or something.

I think the new hardware for inverted black and white provided better solid black uniformity rather than enabling the mode to exist.

Originally Posted by tomsem

BTW, have we settled the issue about whether it has plastic or glass panel or whatever that heated discussion was about from the early reviews?

I don't think so. One person that opened it said he couldn't tell.

There has been a claim that the waterproofing is provided by circuit board coatings and a gasket and that opening the PW4 does not compromise the waterproofing, so maybe someone that can tell will have a look. It is supossedly very easy to open.