Essential - Absolutely the best!
Sure its a little pricier than the average ap. But its also very clear that the developers of this ap labor for love. It must have consumed thousands of hours to develop the ap and countless more to maintain and constantly improve it. Vale la pena (its worth it). In my opinion you wont ever regret purchasing it (or one of its less costly, but a little less extensive brothers) It has helped me immensely in learning and improving my Spanish while living and working in South America. And as a bonus its a pretty great English dictionary as well.
Bife de Chirizo about
English Spanish Dictionary, v7.8.2