I've sent 3 to my home address for my wife and kids and I was very surprised at the quality and speed of delivery.
They're able to do it because of the sponsors. Mistubishi and Expedia foot the bill for printing and mailing in exchange for space on the front and back of the postcard. Its pretty unobtrusive though. I've also heard that they have improved speed of delivery and increased the picture size.
Check out the pics above of the app on my 8900 and one of the actual postcards.
I think its a great idea and the app works flawlessly. Check it out at App World or if you have a Storm, get it here: http://mobile.hippopost.com/
Sent from my BlackBerry device on the Rogers Wireless Network