Hopefully these metrics are not "news" to any "hackers" on HN.
1. Bounce% & time on page
2. CPA (cost per acquisition)
3. Growth
But of course this is a broad solution, and your startup will care about different metrics.
If I'm Google, and I run PPC in search engines, my "time viewing an ad" is far less useful/important of a metric than a simple click through rate.
