Ryan,
This module came just in time for us, as we are launching our website today. We do get one error upon applying a coupon, and then selecting Free order and doing Review Order: "We cannot process your order without payment." The page reloads with that message.
Thank you WBR and Ubercart! 
Edit: We're using:
- Drupal 5.7
- Ubercart 1.0-rc2
- Tables API 5.x-1.5
- Checkall 5.x-1.0
- Token 5.x-1.10
- uBrowser 5.x-1.3
- Ubercart Mod: Custom Price
- Ubercart Mod: Free Order
- Ubercart Mod: Linkpoint API 5.x-1.0-beta4
- Ubercart Mod: Store Coupons 5.x-1.5 (aka Improved coupon discount 1.5)
- Info about coupon applied during the order:
- Coupon gives 100.00% discount
- Expiration: Apr. 14th, 2010
- Weight: 0 (also tried -10 and 10)
- Minimum Order Amount: 0.00
- Maximum Number of Redemptions: 0
- Maximum Number of Redemptions for one single user: 0
- Restricted to one product
- Info about coupon applied during the order:
Our on-site programmer looked at it, and he said it seems as though the coupon isn't being applied properly, and thus the error message is thrown by Free Orders. Any help would be appreciated. Thanks!
Joined: 01/30/2008