All my presented models were modeled in Autodesk Inventor. Drawings were made and sawed as DWG, Autocad drawing format as well as DXF, common file exchange format. The last was saved as version 2000 and imported - opened in VCarve pro. No problems here. Than Edit - find open curves and close them, nest, add tabs, calculate toolpaths. Voila. Parts were ready for milling in couple hours. Before VCarve it took me ages (drawing tiny circles to trim lines in function of tabs production; picking every individual line for toolpath definition, oh my goodness)
I would not like to start a non productive debate on which software to use. Each person has own opinion and everybody claims his opinion is the best. It depends what you do, what you want the software to do for you, do you know someone that already uses the software - you will need some support, pricing etc...
I have also just started playing with Sketchup but only in function of creating simple 3D objects to be exported into Google earth. Limited succes. I do not know the software yet. Before you start using it you have to check if it is a part/single piece modeller or you can also model assemblies, produce drawings. If the answer is negative then I suggest you do not invest your time.
I pick up software that also provides me good support.
Once I was using Rhino 3D which is surface modeller similar to AutoCAD and very popular. it has large user group, good support good price etc.
Hope this helps.