Hi Tero,
Interesting, since that is where I've always installed IDM and I don't think I've ever had a significant issue. Even my couple of attempts at 8.0 have used this setup and I don't know that I have ever had any "coexistence" issues. However, I can certainly see how it could concern people. However IDM people know that the real interaction occurs in the configuration of the DataSource and the application of the SCA files, which go right to NetWeaver anyway.
Matt