The biggest problem I’m having with the iOS app right now is that special characters added from Unicode aren’t supported well in the app at all. I’m unable to review my Egyptian hieroglyphs because the Egyptian aleph and ayin are both showing up in my phone as identical boxed ?'s. It’s also been known to have problems properly pairing less common diacritical markings with the associated letter (dots under or above, etc.).
Additionally–this isn’t exactly a technical bug so much as a learning technique bug–the typing/tapping tests are fine except that you can solve the answer by doing an anagram of the available letters, which doesn’t really help if you’re actually trying to memorize anything. In almost every case, I solve the anagram before I retrieve the word from my memory. For the same reason, I find the current trend for all web courses to include an on-screen keyboard whether one was specified or not infuriating (though I appreciate the ability to specify the list of special characters relevant for a particular language). The automated one is never a complete alphabet and thus runs into the anagram problem, and I would rather there be an option to forego it altogether. In the case of the app, the normal iOS keyboard would, I think, be more effective. It could be coded to appear upon clicking “type an answer” or some similar button and disappear upon clicking a “check answer” button. I imagine probably the original intent was visual consistency and efficiency, but it’s just not working.