The game will come close to a full stop and have to adjust anytime we both deal with a large crowd (probably happens at a minimum 3 to 4 times each level), with framerates in the teens or less.
However, the framerate drops based on the demo is verrrrrry worrisome. My wife and I tend to get games to co-op together and both of us were really excited about having the option with Hyrule Warriors.
I didn't see a thread on this subject, but thought I would share my impressions.