Steem as (the only) auth option requires the user to undertake more steps as in most cases we need to verify the account being created is legit, to avoid spending RC for scammy or duplicate accounts.
I understand that Steem account may remain anonymous or it is not simple to see whether a person owns more accounts at the same time. I suppose that you will gain access to some personal information of the user through the OAuth provider. As it may give you a better idea who is the owner of the account, it does not solve a potential issue of duplicate accounts.
I believe as a user I'd prefer straight forward ways to try out the platform before deciding if I wish to use it or not.
Is the interface going to be viewable by logged in users only?
Nope. The interface is going to be public, but to interact with it you of course need to get in first and social auths allow you to do that almost instantly
Are you going to publish a post every day till Steemfest?
I will write about the most critical points until SteemFest, not sure if every day, but I'll try. I will also keep providing previews of utopian v.2 after the SteemFest until I can give out a full picture, in small pills :)