I see nothing in KYW that Anki didn't do better at... And Anki is free. AND Anki's iPhone app is better designed.
On this iPhone app there's no space for notes on the answer side of the card, there's no choice of memorization techniques, and you can't pick up where you left off if you have to close the app.
At least the app is free, but KYW itself isn't. Take my word, download Anki. Anki is free and uses a handy memorization technique that allows for better memorization. Plus Anki has way more notecard packages you can download and way fewer bugs.
One star unless significant improvements are made.