I think you did an EXCELLENT job walking the user through the tasks. Instead of going about it from the engineering stand point, and creating a dashboard to manage your cards (ha) you lead me through real use cases and I was able to create a card with little effort. I'm a firm believer when a user goes online they become dumber and just start clicking buttons. Again, I was lead through the app with big fun icons and steps that had bright "Next" buttons. A 5 year old could have created and shared a card, that's awesome.
I also liked how you explained the privacy setting on step 3(?). I was thinking it, and right next to the 'Next' button was my answer.
With that said, I thought there were a few pages that felt cluttered. The share page, for example. This is your viral channel and maybe the most important step (depending on your goals) so I would make this the only thing on the page (or bigger). Removing some of the content on the right and definitely at the bottom might prevent people from not doing that final, important, step.
Also, on the share page, have you thought about an email form with a pre-filled message and the link inside? We have found (slightly different use case) that most people don't even care about changing the message and having this form just reduces user friction. However, I can see the advantage of letting the user use their own email client to..