Here's some information provided by Alan Silver about the greatly improved performance in IIS 5.0:
Microsoft did some tests on ASPs vs COM DLLs in IIS5 and IIS4 (there's an article on MSDN with the details). Basically, it seems that the ASP engine in IIS5 has been improved so much that code in ASPs actually runs faster than the corresponding code in DLLs. DLLs have other advantages, such as security and so on, but the issue of
speed is not so clear any more. People using IIS5 will find better performance using plain ASPs.
Obviously, if performance is really an issue, then DLLs written in C++ would be much faster still. Then there's ISAPI which is even faster, but that's serious stuff and not nearly as easy to write as ASP is.