K relaxes the traditional APL constraints on "rectangular data", which makes it comparatively quite good at dealing with text manipulation. I frequently use K for working with text and it works nicely. Anything you can represent as a list structure can have all the traditional APL-ish tools brought to bear on it.

As for "other things", here are a few K sketches I've written recently:

- generate random island shorelines:

http://johnearnest.github.io/ok/ike/ike.html?gist=629a86c257...

- animated holiday card:

http://johnearnest.github.io/ok/ike/ike.html?gist=e5fdbb8724...

- an implementation of the arcade game "Snake":

http://johnearnest.github.io/ok/ike/ike.html?gist=ead275c529...

And that's just me! There are many interesting examples and essays here: http://www.nsl.com