Sorry I missed your post GB. Yes, we used it and it is as good as I had hoped. Easy to use, easy to pay (Paypal) although you can't store your paypal name/password which is a little bit of a pain. We sent ours 2nd class and all were received and normally within 3 days. On returning home we saw a few we had sent and they are really excellent. People seemed to love getting them and those who didn't understand how it was done put it down to "you know Keith and his computers"!!! One lady told Steph that the picture "really looked like you"!!!
In summary, it's fab - not only the novelty of sending a postcard with you & co on it, but the speed of delivery (and from some countries the fact it arrives at all) - the price (cheaper than postcard + stamp in some countries), not having to find those, and then a postbox - ultimately we sent way more postcards than we usually do, and that sums it up really!