Along the same lines as the recent moderator votes, I'd like to see the SO team put up signficant new features or changes for votes before implementing them. The votes and comments would serve as feedback to the planned features. This feedback would be used in conjunction with the team's internal planning to decide on what to develop and when.
Perhaps, the planned feature list could be put up as a series of answers to questions to get feedback on importance and desirability. This would allow the community to help direct rather than react to changes in the system. For example, post "Planned Features for October" (probably too late for September) and lock it to the front page of meta. Put your planned features in the queue as they come up and use votes/comments as a guide to schedule/improve/drop planned features.
The way it seems to work now is that if someone posts an idea that the SO team agrees with it gets done, but there isn't any way to gauge the community's input in the same way that we had with UserVoice.