The target is only win2k3 in the kernel. Everything else is open to discussion (in fact, IMO even the kernel compatibility is open to discussion)
You should, and must, provide as much functionality as possible with the latest versions of Windows.
You can still provide many of the capabilities of Windows 7 using only an NT5.2 kernel. It's only the internal architecture which limits this, and in terms of many win7 capabilities, this kernel isn't a limiting factor.