There are two versions of Sho available; one built on IronPython 2.6 and one built on IronPython 2.7. Depending on your usage scenario, you will want one or the other; the information below will help you decide.
Sho 2.1 on IronPython 2.7*
This is the version you'll want if you plan to use the Python Tools for Visual Studio IDE for Sho, and/or you want the latest version of IronPython (2.7). Note that since this latest version of IronPython is distributed from codeplex under a different license, this version of Sho does not ship with the IronPython bits; you'll have to install IronPython 2.7 (from codeplex) separately before installing Sho. An advantage of installing IronPython in this way is that the Python standard libraries will be available to you as well. Note that if you're planning to use PTVS you need to uncheck the option in the 2.7 installer for the Visual Studio components; that option conflicts with PTVS.
Sho 2.1 on IronPython 2.6*
This version is fully self-contained, in that the essentials of IronPython 2.6 are included (just binaries, not the standard libraries; if you want the latter you'll need to do an install of IronPython 2.6 from codeplex and point your Sho path to the libraries). This is the version you'll want if the IronPython 2.7 license on codeplex is not compatible with your needs. This is also the version you'll want if you want to use the HPC or Azure packages for Sho - we'll be upgrading those in the near future to work with both versions, but for now they will only work with the IronPython 2.6 version.
Installer for Sho 2.1 on IronPython 2.6 (self-contained)
OS: Windows 7, Server 2008, Vista, or Server 2003.
Dependencies (Sho 2.1 for IronPython 2.6): .NET 4.0 or higher.
Dependencies (Sho 2.1 for IronPython 2.7): .NET 4.0 or higher, IronPython 2.7.
*This library includes parts of the Intel Math Kernel Library. For more information about the Intel Math Kernel Library, please visit http://software.intel.com/en-us/intel-mkl/ .