Originally, I really wanted fun RSVPs. The madlib style ones suggested in this post were amazing, and I even mocked up a design. Ultimately, it would have cost us about $50 to do RSVP by card instead of phone/mail. So we went with our online RSVP.
I still wanted some fun language, but we ultimately kept it simple:
Google Forms to set everything up. We linked it to our wedsite URL and then we were good to go.
In retrospect, I'm sad we didn't use RSVP cards, but since I just spent $200 on paper lanterns, I'm glad we saved that $50. The RSVPs are just starting to come in, but so far nobody seems to have a problem with the form. They are also using the response box to write notes to us, which is great, but I wish we had put in a separate optional box for notes. So far, nobody has not written their name, but I'm waiting for that.