First of all, I am a BIG FAN of your service!
And what you read below is a small suggestion from your big affictionado.
I want to know if you run analytics on your site.
If you don't please go to SlideShare.com and check out Dave McClure's slides on the 'Startup Metrics'; it is a must-see in this century.
Now if you've already done the analytics, check how long a user would stay on each page. I am presuming the check out page would be among the top of the list.
And as a moo fan, I think I know why: the promo code
Every time I order moo card, I have the problem of not being able to find my promo code; I either gave the card away because my friend was interested in moo card or lost it with the box.
But the fact that there is a promo code somewhere keeps me from pressing that 'order' button.
Sometime, I leave it open for a few days and then my browser crashes.
I even think your sales might improve by eliminating promo code; at least, someone like me should order moo more frequently, if we don't have to go out looking for promo code.
Of course, I am nit against special promotion all along.
I think promo code would work for something that you would buy only once such ad application software but not for something you would buy repeatedly.
To boost loyalty toward such products points/milage system work better.
Each time you order a moo card, you would get points that is recorded on the server that can later be used for an extra print, rush print, etc. So people know the more they print, the more they get. And they don't have to halt at the ordering page worrying they are missing something but they can confidently press the 'order' button knowing s/he has the best deal.
I think I'd be eligible to upgrade my order to overnight shipping for this tip ;-) but I will give it for free as the present for your 3rd birthday.
I think this tip would work not just for moo but many other services which isn't betting their revenue on unused promo code. ;-)
Nobuyuki Hayashi aka Nobi