The PostCSS system will quite happily play nicely with other plugins, be they Gulp-based, or using another task runner such as Grunt or Broccoli. This opens up a real world of possibilities, limited only by your imagination! There is one small but important point, though—it makes it crucial that we not only optimize our processor output (as we have done), but also fine tune it to ensure that we've added functionality that suits our needs.
So, what can we add? Well, here's a starter for ten: how about compressing images? Another common task relates to adding responsive content—we've already covered this earlier in the book with the postcss-responsive-type
plugin. We could take that further, by adding a task that resizes images automatically to different sizes; we can then use these as appropriate in a responsive site.
Ultimately, it is up to you—as time goes by and you get more accustomed to using PostCSS, then it is likely that you will find yourself using some plugins...