Templating Modules are a bit like editors. Every web application developer has a favourite one. And every template system is someone's favorite.
Mine is Mason. But not because the Perl MVC tutorials are full of examples using Mason. Not because it's the fastest (use xSlate if you want to trade speed for flexibility). Not because it's the most popular. It's my favourite for a very plain reason: It makes me more productive and allows me to develop web GUIs using all the powerful features a programmer should biterly miss if they are taken away. That includes writing Perl code :P
I never heard of a business that went down because they didn't have fast enough CPUs, so I'm not fussy about trading a few CPU cycles for elegance, ease and speed of development.
Enough talking. Here's my contribution to the template holy war and Mason lobbying presentation: