Another stupid idea by yours truly. I don't know how long the log-in loading screen lasts on most sytems, but perhaps instead of just a MOTD, give the the user a little poll. Somthing short and sweet and easy to answer in half a second. For example, What's more important: X or Y? And have X or Y be chosen randomly each time from a list of issues and open projects. With thousands of users you should be able to grap what is important even if each user is comparing two random things. Overall, you should be able to judge "The widom of the crowd" better than forums (which tend to be filled with opinionated people) or the voting system (which suffers from user apathy and misinformation). Integrating feedback in a non-intrusive way might weed out the noise caused by self-selection.
It also could go a long way in making people feel like linden labs is "listening."