Silo is a $159 (you are charged in $USD) professional 3D modeling utility that comes packaged in a 7.2MB installer. It is one of the most comparatively expensive tools I have ever used. But of course, it's not the bytes that count: It's what you do with them. Silo leaves out a lot for a tight focus on the core essentials of classic modeling. See all: Software Downloads.
In recent years, quite a few tools have tried to make the arcane art of 3D modeling easier. There's the free SketchUp (and paid SketchUp Pro) with its easy-to-use approach, great for architectural modeling and other objects. For easy character modeling, there's the free DAZ Studio, and paid DAZ Carrara. Each of these two-tier packages (free and paid) has its own online repository with thousands of models you can build on and use in your creations, and are powerful and mostly beginner-friendly.
By comparison, Silo has only one version (paid), and its model repository is a wiki page with a handful of models. Not only that, but its last version was released in 2008, with no plans for a new version. I experienced some problems running it on Windows 7 64-bit: The application crashed several times, without any error message - the window just suddenly disappeared. It doesn't support model rigging or bones for posing, nor does it let you save morphs for facial expressions like Carrara does. But it is also free of clutter, highly customizable, and fast; it's easy to focus on the essentials of 3D modeling. Silo also exports standard model files, such as 3DS and DXF so it doesn't lock you into proprietary file types.
Silo's best feature is called subdivision. Make a cube, and press C. Suddenly, the cube's sharp surfaces become rounded. Press C two or three more times, and you have a ball. This seems pointless with a cube, but it lets you create beautifully organic models from a handful of basic polygons. You rough in the shape of your model, press C, and your blocky, angular model suddenly becomes smooth and organic. You can press V to undo the subdivision, or keep tweaking the model in its subdivided form. Free modeler Hexagon from DAZ offers a similar feature, but with a much busier (and more full-featured) interface.
To begin using Silo, I watched a series of tutorials by talented modeler Glen Southern. These 11 videos take a few hours to watch and use for practice, but they explain 3D modeling basics in a clear and simple way while showing you around the sparse Silo interface with its myriad keyboard shortcuts. I then tried my hand at creating a simple dog-like creature. Silo behaved well for the most part, but, as noted above, it did crash two or three times without warning. Fortunately, it auto-saves the current model, so I did not lose much work.