I used it quite a bit right at the beginning, when it was transitioning from being a "Pre-HTML Processor" templating utility to a proper language.

The syntax was nice and easy to pick up. The rest was pretty bad, a lot of security was left to the developer following best practices.

It improved with time, but it had already left a bad impression on me.

I know it's still popular, as you can tell from the downvotes.