Toodledo combines due date, priority, and 'star' into a single measure called "importance". I find this fantastic, because it takes far more concrete measures and automates the ranking of tasks and takes a significant burden off me.
What not even Toodledo does, however, is give the user some kind of control over how "importance" is calculated.
For instance, I have my own measures - "impact" and "effort" - and I can build a tag system that with some measure of duration and due date. But it's a pain! And it's error-prone!