1. One difference is that a different key pair is used for every domain so you don't have to worry about your public key being used to uniquely identify you. Also, I think this is easier for novice users than creating a cert.

2. I plan on adding in an import/export feature for the next release.

3. This should be more secure than passwords because the only information that the server gets is your public key, which of course is assumed to be public knowledge. No more wondering if the website you're using is properly storing passwords.

Thanks for the questions.