More or less useful, but in some language combinations (e.g. French -> German) it gives only one word as translation (from Google and Microsoft) and as we all know, a word has almost never just one translation. Given more translations, an intelligent reader is able to choose the translation that matches best.
This is maybe not the fault of imTranslator but of the underlying dictionary machines, but unfortunately, this way, I cannot recommend it to my pupils at school.