I love that it's easy to customize, you can easily add your own modules or plugins if needed! The support team at composrsolutions are fantastic too - they're always willing/able for help when we need them most (and not just during business hours!).
It would be great to have more in-depth tutorials available online so people like myself who aren't technical experts could use this as well without needing someone else there with us every time something goes wrong :) Currently using composer cms because of ease of customization & plugin management but really any content manager will do fine once installed properly :). We've been able solve all our website needs through compositionerscms from blog posts / pages created by users via user accounts to ecommerce products sold directly within site itself.