From my collected emails on the subject of what tools and stats are most vital, comes a set of questions like this:

I'm very confused with all the stats and ranking options... I'm not sure I have time to follow all of them. Which one or two are the most important? Isn't traffic, people actually visiting your site, the real bottom line?

Sure it's more important to get visitors to your site ~ if they arrive there looking for what you've got.