We'd love the ability to use a coupon code on "Secret" Prices at checkout - field is missing even though coupons are present for the products used.
We use Secret prices often for upsell bumps and funnels to track the purchase path or to offer sale prices in sales funnels, or additional discounts to members, however we've noticed that because we use secret prices the Coupon Field is not visible at the checkout.
This also disables us from being able to test funnel processes with a 100% OFF coupon.