1. It would be nice to show a message on the checkout page when an invalid or expired coupon is entered.

2. Scenario: When using both a discount (ie: quantity discount on one product), and a coupon discount code (ie: $10 off total order with coupon code) where both discounts CANNOT be used on the same order... When the first discount (quantity discount) is applied, it shows on the cart page, but when a coupon code is entered on the checkout page, and has a higher weight, it overrides the quantity discount. However, when a user browses back to the cart page, the quantity discount still shows, not the coupon discount just applied. Then when the user continues again to the checkout page, s/he needs to enter the coupon code again.

3. It would be nice to show the discount code textarea on the cart page, similar to how the uc_coupon module works. This would allow one to use PayPal express checkout.

... just some suggestions.