MinGW is compatible, yes. I am under the impression that other versions of VS aren't. Correct me if I'm wrong. Confirmation if I'm right would also be appreciated.
Comment on Re^6: "Lag" of modules in ActiveState ?
Yes - that's what I was unsure about. On first reading I thought you were saying that Visual Studio 6 must be used (which would be incorrect). You weren't saying that (you were correct :-)
As regards the other Visual Studio compilers, my hunch is that VC 7.0 (at least) would build Win32::OLE for ActivePerl, but I haven't checked.