@ Geoff, the one thing you’re “missing” is that you need to make sure you target the right framework version when you create a new project under VS2012.
As Gus points out the support page here leads you through the three things you need (Visual Studio, the netmf core SDK, then the GHI SDK). Once you’ve done that, either VS2010 or VS2012, you can create projects that target earlier framework versions.
netmf4.3 is not supported by any GHI board at this time. There is a community 4.3 port for Cerberus family. So unless you have this, your app will still be targeting the 4.2 framework. Create your project, and then in the project properties make sure you target the correct framework version for what your board supports.