I have to say that the Warhorn system seems fine to me once you are setup.
1: create an account, once forever.
2: join an event by following.
3: when games are opened, sign up.
Usually these steps are weeks or even months apart, it's just that
@Newt and
@dr_mitch have done this at speed so 1,2,3 seem very close!
I did 1: years ago.
Many organisers want/need/like to know who's coming before they do the final release, often to prvent people signing up weeks in advance and then forgetting all about it.
The Albacon system, which was coded for the event, I believe, follows the same pattern..