Interior Designers and Architects have SketchUp, product designers and builders now can use AutoDesk's 123D. It is based on AutoDesk's famous Inventor application. However instead of serving the needs for engineers and designers alike, 123D is cut down tool-set wise to what builders and modelers only need. This means while you have all basic standard geometry creation tools such as extrude, loft, fillet shell, and others, finer control about details such as radial fillets etc. is not given. Stress-tests or thermal tools are of course not included. This also enables Autodesk to offer this product for free.
This might look like a limitation, which it is, however in addition 123D features a fully working parametric design tree system, with an assembly option, and perfectly working snap, grid and geometry constraints. Those tools are essencial to build and think through a product design without the need to rebuild geometry. In parametric modeling, unlike in Blender, one builds geometry through utilizing constraints and measurements which in a nested approach build the model. Changing the model only requires changing the modeling tool settings.
The following screenshot demonstrates the different steps, from drawing a circle, extruding it, deforming the end edge, and applying a UV texture.
The interface is very clean, uses a below the mouse pointer geometry sensitive radial tool menu. The presentation modes allow wireframe and shaded textured view with realtime shadows, ambient occlusion, onscreen anti aliasing, and ground reflections. With a slower 3D card those options should be turned off to increase screen refresh rate.
Similar to Google's 3D Warehouse, also Autodesk created an online infrastructure where you can send your 3D models to, or download models. However they go one step further and also connect you with the rapid prototyping and 3D industry ranging from 3D printing to 2D laser cutting. Autodesk's strategy is to tap into the potential of hobby modelers and builders which do not need high end CAD system but would use the readily more accessible and affordable 3D printing services.
123D native file format can be used to store your design on your computer or to upload it into the online 3D warehouse. If you want to export you model into a different application you can select from a wide range of options such as STL for 3D printing or to import it into Blender and STEP a common NURBS exchange format. OBJ is sadly not supported, at least not at the moment.
The program is in beta and thus it can be expected that further tools will or might be added. It is currently only for Windows and not OS X while a petition for an OS X port is already on the way.
As a free product with decent solid modeling tools and an amazingly well working construction tree, this is a great tool for everybody who like product modeling but does not want to shell out few thousand dollars for the professional applications.