I found that using Smarty with PHP, sometimes extra time will need to be used for
1) using quite different syntax than PHP itself
2) need to check small cases, b
I don't like templating engines. I find them very lossy and resource-intensive for PHP.
With MediaWiki, around version 1.6.x we backed off using Smarty by default and just use PHP's built-in templating, with a great improvement in performance.
I've found that most of what people want to do with a templating system (add links, change colors, remove text or sections of the page) are better done with a simple system of event hooks.
Laconica, the open microblogging platform, doesn't do any templating by default. We have a plugin for people who are crazy for templating.