I bought the official leather cover / case for both Kindle 2 and the Kindle 3 WiFi with the lighted gizmo built in. I use them for travelling but not at home. What I've found is I actually prefer to read "naked" ...
the ereader, that is, not me!
So for all three Kobos, I didn't spring for a case. As much as I like the simplicity of the Roots pouches, I just can't bring myself to spend $30 for one. And the book-like one -- which straps the Kobo in all four sides -- seems a bit flimsy.
I may change my mind the first time the cat knocks one of them on the floor ...