This app is invaluable for studying Greek, but you have to keep a couple of things in mind:
1. To set it up requires the desktop version of Logos Bible Software. This isn't a big deal for me because I already use and love the software, so the setup was pretty easy, but if you're looking for a completely stand-alone solution, you need to look elsewhere.
2. The app locks up ALOT. By alot, I mean every time you shut down and restart the app, it locks up. I've gotten used to killing it as a matter of habit now, and it works okay if you leave the card view and go back to the list of stacks before leaving the app, but if you happen to leave the app while viewing a card, you'll have to force quit the app to get it to respond. This should be fixed.
3. If you've marked all of your cards as "got it" then the app will start reviewing all of your cards for you. If you subsequently miss one though, beware of marking it as such, because then that will be the only card the app will show you, at least until the next day. Use "got it" sparingly, and only when, as the tutorial says, you REALLY know the word.
That said, I still recommend this app. The layout is clean and having the cards in digital format is far better than having hundreds of notecards to carry around.