I have an account that used to admin Google Apps. If that account is available as a choice to log in -- doesn't matter if it's logged in or not, only has to be on the account select -- then none of my accounts can log in to Hangouts. Seems it's trying to redirect me to enable my Google Apps account again, then complains that only an administrator can perform that action.

On the surface though, yeah, if you take some screenshots it looks like really good UI. The follow through is generally garbage though. I think it's fair to put it on the site.