Update: Manuel himself wrote a great post about this. Go read it.
We run a monthly mastermind with some friends to discuss how our businesses are doing and give each other feedback, and yesterday's was a superb one.
It led to an insightful discussion on prioritization and deciding making.
His approach boils down to answering this question:
If I fail to achieve this goal, what would be the most likely cause?
Working backward from there, he defines projects and tasks.
I want to apply this to Mailbrew's roadmap and look at things from a different perspective. We are product-people that love building cool stuff, but not all problems are engineering or design problems.