Hi guys!
I'm using jbpatch for some days and it is a very good improvement over plain vanilla Amazon stuff, mostly hyphenation and alignment correction. Thank you a lot Ixtab.
I think a great improvement could be a patch to select a font (I know there is a font hack to change Kindle font, but not a selectable one by menu).
Another improvement could be change interline from 70% to 200% or so.
And the ultimate improvement, ability to have two columns.
I know those can be very difficult things to implement (mainly third and then first ones) but then Kindle Framework will be the best reading app ever done.