The wife & I attempted to use SP at Lowes last night (last day to obtain Gold status). The first attempt failed. She tried it again, and quickly got a notification on her phone indicating it was successful. However, the terminal did not respond immediately, and eventually timed out. The cashier asked if we used the phone, and confidently stated that they are not set up for mobile payments. It took a few minutes of arguing with 4 employees before they would cancel the transaction. The wife also received a notification of the cancellation on her phone. We left and went to Home Depot. No issues there.
I've had more trouble with cashiers assuming it won't work. I usually try to 'swipe' the phone before they get a chance to see what I'm doing, and start telling me "that doesn't work here."