For me I would need to know more about what you are working on or hope to be working on before I could whole heartly recommend investing in learning mod_perl. I have been using mod_perl since at least 1998 and there is a lot I still don't know about it. I have done most of my work with it at the templating/framework level with modules such as HTML::Embperl and Apache::ASP. Based on this I would recommend mod_perl if:

• You have a development machine with root access
• You have at a minimum, access to the log files on the production machine
• You have some way to stop and start the mod_perl (httpd) process on the production server easily.
• You are doing large scale applications.

mod_perl was complete overkill for the first project I used it on, but for me it was more the fun of learning it then it was the need for the performance. If you are going to do large scale developemnt and need the performance make sure you read the mod_perl Guide before you even start to install it or work with it.

mod_perl is awesome if used correctly, but can quickly create a lot of head scratching that you might be able to avoid if you don't need the extra power it provides.