I like that it allows us to easily manage our website translations from different languages, also makes the job of maintaining this translation easier with its automated features which help me quickly add new language versions or translate existing ones (in minutes).
It has some bugs here and there but nothing really serious so far as long you have enough experience in writing plugins/extensions for this CMS. We are using contenido to maintain several websites we own. This platform facilitates managing our main site from one place without having too much work involved once every few months while making sure all other sites remain up-to date.