One of the main advantages of mod is the increase in performance over traditional CGI. Below are results of a very crude test. The test was done on a 1.2GHz Pentium machine running Red Hat Linux 7.3. Ab was used to poll 4 kinds of scripts, all of which imported the standard cgi module (because this is how a typical cgi script begins), then output a single word ‘Hello!’. The results are based on 10000 requests with concurrency of 1.

Standard CGI:                         23 requests/s
Mod_python cgihandler:         385 requests/s
Mod_python publisher:           476 requests/s
Mod_python handler:           1203 requests/s

The publisher handler is a good way to avoid writing your own handlers and focus on rapid application development.
It was inspired by ZPublisher.
PSP handler is a handler that processes documents using the PSP class in mod .psp module.
CGI handler is a handler that emulates the CGI environment under mod .

可以看到，Mod_python在web应用方面还是有不错的表现的，况且它现在也是apache的一个子项目了，ViewCVS之类的开源项目也是基于Mod_python进行，相信以后会更好的。