I have an Aura and I bought this after the first week:
http://www.geckocovers.com/screenpro...kobo-aura.html
Been using it ever since and I have no issues with screen responsiveness. I have no bubbles and I think it even helps, in the Aura, to not notice the scratch like pattern on the top of the screen.
I'm not sure how it works for the Touch, but one thing is for sure, I feel much safer using my Kobo without it's cover around the house and that should count for something.