2 million downloads a week is hella impressive.  It also states Sketchup had around 30 million users in 2011, which I think clearly makes it the most used 3d software. If you added up all of the Autodesk products together, I don't think it would come close to those numbers.  I never really liked Sketchup, because it's really not friendly with other 3d packages, and doesn't create good topology for exporting.  It's a good CAD software though.

---

Tools :  3dsmax 2015, Daz Studio 4.6, PoserPro 2012, Blender v2.74

System: Pentium QuadCore i7, under Win 8, GeForce GTX 780 / 2GB GPU.