Pretty much the same for me as @Poodlemom1--returned all three PWs and got the Fire HD. The Fire HD is great for reading, but not much else. I've had an iPad 3 for quite some time and it is terrific for reading too, as well as all the other tablet stuff! I can't speak for the mini as I haven't been able to see one, but I'm leery of low pixel density. My iPad 1 was terrible for reading because it had even lower pixel density than the mini. You will just have to look at one to see if it woks with your eyesight. But I will say that the Kindle for iPad app is tops. It even has some things the Fire HD reading app lacks like screen brightness control and two column landscape view.

EDIT: And it is a lot easier to load alternative reading apps on an iPad than on a Kindle Fire as iTunes sells them!