I\'m pretty well up to speed on general web programming languages, but one of the tools I\'m working with right now is in CGI. All I can tell is that CGI scripts are quite slow.
I know of 2 projects that are being actively being developed that still use CGI scripts to good effect.
The first is Webmin a web-based system administration tool that I've been using for years.
The second is GitWeb which allows you to setup a web interface to your Git repositories.
As to the speed of CGI (or lack thereof) I can't really comment on that. From my experience with Webmin I can't say I've had any issues on that front.