I've been looking at this a bit more over the xmas break and have discovered that it doesn't work for ecommerce 0.5 either.
My client will need this working this week, so if anyone can help me get it working on ecommerce 0.6 beta or an alternative module that will acheive the same thing, and is looking for a paid job where you will work along side me to get it done this week contact me!! You would need to get back to me today.
the coupon idea works pretty well. I send it out in my e-commerce school newsletter to let the students now about hosting discounts and other stuff from related sites. Keeps customers reading my newsletter and visiting my site.