Just read a newsgroup post by MS' Jim Hogg mentioning what sounds like a really cool feature and very useful debugging aid: Customer Debug Probes. Here's a quote:
"(In passing, I'll plug the "Customer Debug Probes" feature, in the "Tool Developers Guide" folder -- coming soon. With a config file, you can turn on extra tracing that helps track down obscure problems encountered during interop with unmanaged code. PInvoke mismatch on stdcall/cdecl and similar)"