What email metrics do you use?

Vertical Response talks about email metrics that are useful on a dashboard.
Metrics are an ongoing challenge for all marketers. The underlying need for metrics is to evaluate how effective a particular marketing program is. Picking metrics involves understanding what the goal is for a particular program. If your goal is brand recognition then perhaps sales and click-through figures aren’t a good metric. If your goal is sales then opens is not as good a metric as average order value or revenue per email.
Measuring email success is important. But how you choose to measure it is a critical decision. Too many marketers just use canned metrics and don’t think about what they really want to know.