Some people think that SketchUp is too simple, others are afraid that they’d need additional extensions in order to work effectively. But despite the huge number of various plugins, SketchUp can do a lot without them.
SketchUp's interface is simple, not overloaded with features, and works quickly. However, there is also a reverse side of the coin. There are a lot of subtleties in the program interface that you need to know in order to be able to use it.