It's pretty good at European languages, but still terrible at Arabic and Japanese. The system still has a very shallow understanding of the content. One of my primarily Arabic-speaking colleagues was actually offended by Google Translate butchering their language so badly; their culture places a relatively high value on poetry, calligraphy, etc.

As an exercise, try translating your search queries into Arabic before searching. Then, let Google translate the results for you. It is hilarious.