I still love my 2Ki. If I had to upgrade it would be to a K. Keyboard (3). I like the physical keyboard and use it daily, if only to jump around in the books. Yes, I don't always read begining to end, sue me.

I also like that the keyboard raises the screen higher while reading in bed

. prefer page turn buttons to touch screens. Easier while holding the K by the sides, finger/thumb already on the button. Having held and used the 3K (my mom's) I find it lighter and easier to hold naked than my 2Ki. My K is slippery and needs a case or I feel like I would drop it. The 3K has a rubber feeling back and the grip feels much safer.
It is wonderful that Amazon has so many options now availble for people to choose from. Budget friendly, wifi for never leaves the house, 3G for those who don't have as much wifi available, buttons, no-buttons and now a touch screen and full color. Luck us!