i create the .NET 4.5 assemblies for NetOffice today and the upload is currently in progress.
.NET 4.5 may an in-place update but secure is secure hm 😉
the 1.5.1 [RC+Office 2013 Support] release includes the assemblies/examples/tutorials in .NET 4.5
btw: CoClasses like Excel.Application has static methods now for easy access to all the running objects. as example:
Dim app as Excel.Application = Excel.Application.GetActiveInstance()
use the GetActiveInstances() method to get all running objects.