I gocco'ed my wedding invitations. I made two designs that I drew myself, so invitees got one of two designs.
It took a few mistake tries to get it right, but I was pleased with the results once I got a good burn. My recommendation to people buying used goccos is to check the sponge/print pad. If it is compressing too much (ie the sponge is old) you won't get a crisp burn or print. I made a new print pad out of foam that I found at Orchard hardware.
I got all of the supplies from paper Source and lined my envelopes with some paper I found at another art store.