Got my K4 package yesterday. Actually 3 of them. I was planning to get one for myself and two others as gifts.
The screen is definitelly darker than my year old K3 making the contrast bad and as some of you already said it makes reading quite difficult in worse lighting conditions. This applies to all 3 pieces. Besides that I have probably received devices from the batch which is not in Amazon system yet so I was unable to register it and spent an hour talking to four!!! different CS people. As I am living outside of US you can imagine that the call was quite expensive as well. Just call me unlucky
Tomorrow I am going to compare mine with one of my colleague's who bought it several weeks ago and then I will decide what to do with them. Right now I feel like just returning them. What a shame, such a nice looking device.