There are many AutoCAD blocks/nested blocks Sketchup does not import. If exploded, model becomes messy. So what is the ideal way for importing AutoCAD file into Sketchup? And visa versa; best way to import a Sketchup file into AutoCAD?
As to blocks per se, the only issues I know are that SketchUp will not import unnamed blocks. Many AutoCad plugins create these. To import them you must rename them in AutoCad.
Surfaces and Meshes are the most glaring object types that do not import into SketchUp.