Two to three hours of reading and I'd adapted from the K2 to the K3 buttons with no problem. They will become second nature rather quickly for most of you I think.
On the other hand I have to agree with Harry about the fiddly feeling the K3 gives me, not only the 5 way but the entire device. It is so small and thin that my, not so large, hands feel like they are almost cramping trying to hold and use it. I'm used to the K2 with the Amazon cover and remember that it also felt small without the cover. Of course I spent much of my life working with my hands doing manly stuff.
Until the new cover comes I'll just have to put up with that delicate feeling.