coupon not working

i created a coupon for one product called free sample.
i valued the coupon at 8.49 and the free sample at 8.49, with free shipping.
the settings for the coupon allow unlimited use of the coupon, one per customer.
when the customer redeems the coupon during checkout, the 8.49 is crossed out and the green 'FREE' icon is showing. with the correct redemption code everything seems to work, but i can go back and do it again and again.
i have tried valuing the product as 0.00 same thing happens, maybe the green 'FREE' isn't showing up.
the whole thing is not supposed to be this complicated, but nothing i do seems
to get it implemented correctly.
zen 1.3.7

Discount Coupons can be set up for:

1 Discount Percentage

-- OR --

2 Discount Amount

-- OR --

3 Free Shipping

You cannot combine these together in the same Discount Coupon at this time ...

The product i mentioned has always free shipping. coupon or not.
i don't see why the setting up of the coupon to the value of the product
won't allow it to work. In any case, i think with all the posts about coupons
reflects the need for more development.
The ultimate question, hidden in this coupon stuff, is how to implement a
free sample correctly. it has to do with coupons right? the free sample has to have a redemption code, so coupons have to be involved somehow.
If you could let me know what others have done to implement the free sample idea, i would be a happy zenner.:smile:

Set the Coupon as the value of the Product ...

Set the restrictions to be:
Top Cat Deny
Product (whatever it is) Allow