Yesterday, I stumbled onto this wiki page with a transcript and an MP3 recording of the first brownbag meeting between Linden Lab and third-party viewer developers. The third-party developers were well represented, with some people fairly well known(McCabe Maxsted of Imprudence, Fractured Crystal, Chalice Yao and Lonely Bluebird of Emerald) and several other developers who I'm not familiar with. The Lindens were equally represented, and the discussion in text chat and voice was pretty formal and informative.
The meeting opened up with "What 3rd party viewer features do you think are very useful to users?" and then a Q&A with the Lindens about how the registry process might work out.
From the tone of this first meeting, the Lab might cook up a registry that is fair to all parties involved, including users. The Lab might work closer with 3rd party devs, but not get heavy-handed like the devs feared. Users could get a detailed description of approved viewers along with user reviews and ratings. And perhaps most beneficial, the Lab may finally incorporate some 3rd party features into the official viewer.
So now I'm less cautious and more optimistic about the registry, but there are more brownbag meetings to come and nothing's finalized yet. I'll post when more details surface.