<< SketchUp is very easy to use so it's great for beginners but it's also mainly designed to do boxy architectural shapes and builds everything out of polygons.

The boxy mode is now some avoid by some tricky plugins! ;)
So now SketchUp is also becoming a sort of Subdivision prog! (not so poweful than a real one but as it's so easy...;)
http://evilsoftwareempire.com/subd
http://evilsoftwareempire.com/vertex-tools