@DrLuke: Dig a bit in the forum/wiki, a bunch of people are working on native applications, using a different range of toolkits to interact with the framebuffer. (Or X11/both on the Touch/PW).
It boils down to what your favorite toolkit is: we've got GTK guys, Qt guys, directfb guys (I think), and the low-level guys who like do it themselves
.
Currently, the most fully-fledged stuff is probably the few cr3 ports, and kindlepdfviewer. Although not everything might be handling the K4 fb yet.