Of all the free apps Ive gotten, this is by far the best in terms of available resources (extensive reading library), pedagogical value for teaching/studying Greek and original biblical texts, and usefulness (having a pocket resource that is vast, accurate, and easy to use as a practical aid in personal study and in the classroom).
If youre a student of Greek, in particular, the double screen of Greek and English with a double tap offering parsing, definition, and lex form, is wonderful.
Seriously, get the app, youd be a fool not to.
J.G. Raveney about Logos: Deep Bible Study