My major gripe is how they said this would be this huge community shaped project, yet they have shut out the community for months now. No official word since May, but even before they haven't talked a lot. And this goes hand in hand with how the testers have lost interest and gone quiet after the first months. It should have been in Valve's best interest to poke them and to provide them with material. Can't blame people for not giving impressions when there's lack of content or reason to. Not to mention their controllers are long outdated.
I think the fact that they brought prototype versions of the controllers to several industry events and let just about anybody play on one seems quite a bit more open than anyone else in the industry is. And I may be wrong about this, but I thought SteamOS is in beta currently and could be downloaded for anyone to see and use. Don't know if they have stopped updating it though...
My first response when people complain about Valve's lack of openness is "Compared to what?" If this were MS or even Sony, we wouldn't know anything about it until all the decisions are already made.
I wish I had more information on it too, but it's hard to see the argument that having very public testing of the beta is somehow not a very open process.
As an aside, I am still optimistic. Not as much that the Steam controller will become my only controller (although maybe still!) but that I will now have the option to play M/K games on the couch without issues.