I'm guessing that on the one hand it would be best to keep tabs on everything, but at the same time that causes you the lose focus. At least I've notived that I'm most productive when I focus on one thing at a time. An alternative would be to regularly switch between the different KPIs (Key Performance Indicators, I'm using the term loosely here).
So, what do you consider the most important KPIs for the first 100 users (and which tools do you use to track them)?