Dah Dit to work on my CW for several weeks now. It has worked wonderfully. I was able to learn the characters easily, but the app lacks when trying to learn to hear words.
If you you haven't learned CW yet, there is a dramatic difference in identifying a character and deciphering a complete word. The dahs and dits all seem to flow together at first. So I have been looking for something to fill the hole and keep me moving forward. Well, I think I found it.
Ham Morse by AA9PW is another Morse Code IOS app. The difference, at least for me, is that it is focused on sending letter groups, call signs, and words. You can set it up to send random words, random callsigns, mock QSOs, or even the daily news. I've been working with it throughout the day through my handy little bluetooth earpiece (so know on else can hear). It's been working very well. By playing with character speed AND spacing, I am making progress.