The Translator component is the one you learned how to use in 5 minutes and you have not thought much about it since. It just sits there in almost every project and just works. That is great, that is what a great component should do.
The tricky part is how you build your development processes to work together with the translation process. You will start to notice problems when you have 4 or more languages. What other tools and services should you use? And how do you teach external translators to edit xliff files? Of course your should not force XML on non-developers.
Taking the experiences learned from JMSTranslationBundle, Happyr’s translation bundles and the PHP-Translation organization; I will give you example of a few very concrete processes working with translations in a Symfony environment.