I did on successful transaction with a normal product.
Then I installed recurring products and coupon with Stripe (Plus), the premium version.
And then I started getting the error from the subject after I submit my payment info with two products, the subscription and a setup fee and apply a coupon:
Warning Array Key Exists Error ... the first argument should be either a string or an integer in [...]/stripe.php on line 2384.
I got this in both test mode and live mode and in both cases the credit card fields were highlighted in red when I got this message saying "The form cannot process your payment. Please contact your site owner."
In test mode I see in my stripe dashboard that the payments seem to have gone through despite this error but they didn't go through with this error when I switched everything over to live mode.