I've been running an ASP site for about four years now. At the time it was a great way to have a site with server side scripting with a hosting provider that didn't charge for occasional spikes of high bandwidth.

For me its biggest weakness is the bizzare hoops that you have to jump through in order to do things that are a breeze in Apache based solutions. For instance: at the time I was tryng to build a site that used templates around a file that was included from a variable. I searched and searched across the net for a free example of something that was as simple as <? include("$foo.php"); ?> in php. Here's the best that I could come up with at the time:

<%
SUB ReadDisplayFile(FileToRead)
   whichfile=server.mappath(FileToRead)
   Set fs = CreateObject("Scripting.FileSystemObject")
   Set thisfile = fs.OpenTextFile(whichfile, 1, False)
   tempSTR=thisfile.readall
   response.write tempSTR
   thisfile.Close
   set thisfile=nothing
   set fs=nothing
END SUB
Call ReadDisplayFile(foo)
' Server will ignore ASP commands in dynamic include files 
%>
[download]

Granted this was many years ago, but still. No matter what language you are writing in for an ASP server, you are still locked into the conveluted world of Microsoft's web servers.

The fundamental power of web scripting in Perl (or PHP or Python or C for that matter) is the rock solid foundation that you get from Apache. Apache is a monster app that no one (not Microsoft, not Oracle, not Sun, not IBM) has been able to even get close to let alone touch. Add to that the huge community that is built around Perl and just about any solution that you can find is just a click to CPAN away. On the ASP side you will quickly find dozens of groups willing to offer you 'solutions' as long as they get paid.

Even Asp is better in Perl. Apache::ASP is a wonderful module to work with giving you all of the useful bits about ASP while still in a Perl/Apache framework.

In recent days ASP has had a leg up on the XML support, but luckily AxKit is killer.