Pretty cool - the only people I send letters to are my family so I'd be a little afraid of them recognizing that the letter wasn't written in my (chicken scratch) handwriting. Do you write the letters yourself? I'd recommend adding a screenshot of some sample letters so we can see what the writing looks like.
I'd also recommend letting someone select the letter, enter the message, delivery date, recipient address, etc. before asking for their billing info. It takes too many clicks right now to actually see how the process works.
Agreed. Once they have created something they like and want, its much more likely they won't mind signing up and your conversion rates will be higher overall.
One of the first websites I ever made was doing a similar thing, and I stumbled across it in my backups the other day so I relaunched it just the other week. Www.sendachristmascard.com
Your site looks very good, I agree with the jcbmilgn that it would be good if you could make your order before having to register
I'd also recommend letting someone select the letter, enter the message, delivery date, recipient address, etc. before asking for their billing info. It takes too many clicks right now to actually see how the process works.
Good luck!