i haven't purchased a case but i have the roots pouch - black - it's comfy and easy to carry around and keeps from getting the kobo scratched.
my one concern about a case for the kobo would be having to hold a flap open where as the kobo naked you just hold that and don't have to worry about a flap bouncing back, just wondering if anyone finds that bothersome?
i left the tag on it and may return it and get another but so far so good.
Black Sleeve