I buy wherever I want and format shift when needed. So it's
all about the nice ereader in my case. Everything else is.... easily surmountable.
For my money, the K2 was perfect. The K3 will work if my arm was twisted, but I'd rather not (I have access and experience with the K3)... so I'm hoping the K4(?) is a step
back in my direction, but I'm not holding my breath.
One can always hope, though.