I'd really like to give this a shot but am only interested in trying it on my iPad which can't get iOS6, so unfortunately, rather than passing on this, I am being left behind.
It's worth sending that feedback to Marco. He has said in Build and Analyze that the iOS 5 version is written (just disabled currently) and he is curious whether he should release support for it in a version rev or if he can abandon it.
It's worth trying on your iPhone (if you have one). It uses the text-only approach of Instapaper so screen-size doesn't affect usability the way it does in standard magazine apps.