I have published through IAG. There were a couple of issues that I ran into.
Authentication
If you expect to have single sign-on to the Netweaver portal, it can be a bit of trick to configure. I ended up with a double-hop through the underlying ISA in order to get this to work.
URL Strings
The Netweaver portal seems to generate some excessively long URL strings. Because ultimately those URLs are passed through IIS, I ran into a situation where IIS was reporting "Invalid URL" when clicking around part of the SAP application. There are some specific registry entries to address this.
Hope this helps or if you have specific questions.