VW Machine is not really comparable to Inventor or Solidworks or Alibre Design.
It offers no 3D contraints nor 3D dimensions and so the ability to proof a mechanism on screen is not something that VW Machine Design can do.
In fact all it does really offer for the engineer is a series of 'plug in objects' such as bearings, screws, springs, and a whole host of other hardware/fasteners in both 2D and 3D. These are very useful BUT I'm not sure that they are enough to put the 'Machine' in 'Machine Design'
Alot of these are OK but there are basic elements missing, for example 'Flanged bearings'. I am based in the U.K. and PIO's like the washers are never the right size so I end up drawing my own.
I don't have the Architect Module but I have a feeling that alot of what is in Machine Design is in fact in the Architects part.....I may be mistaken though.
The 3D modelling part of VW is very good, you can model some really organic stuff and it is improving all the time.
Overall I would say that VW offers many different things and does alot of them very well, but the Machine Design bit always feels a little left behind.