Maybe I speak subjective, but my opinion is:
-for ad-hoc analysis directly from NAV, I like to use JetReports Express
-for making a serious analysis, BI4Dynamics is almost indispensable tool (if we talk about quality / price ratio)
Of course, you can make big BI project with perfect analysis, but this can be too expensive.
BI4Dynamics is so easy for using and is not expensive tool. You can find its implementation all around the world.
You can donwload free trial version from www.bi4dynamics.com/.../trial. If you know pivot tables using, you will gonna be very easy to manage it. You have not have the same partner as NAV for implement this solution.