I've been harping about your 3rd point at least since Steak 'n Shake started accepting Bitcoin. If merchants are suddenly able to keep 2-3% of a sale by not having to fork it over for credit card fees, they ought to at least have to option to pass some or all of that along to the customer.
I wouldn't even present it as a 'discount'. I haven't seen Square in action, yet; but, I imagine the customer must be presented with a conversion rate at some point. Imagine you're a Bitcoiner - who naturally has some idea that the current conversion rate is like 105K - and the coffee shop is offering you a rate of 107K to spend your sats instead of dollars. That's a coffee shop I would want to go back to.