For those who saw the description and thought this was an app for singers, its not (not specifically). Its for musicians of any kind who are trying to train their brain to hear and recognize notes accurately. If you find that boring, you wont like this app.
It was really tough at the beginning, because there are no levels. You cant gradually train yourself to discriminate among a smaller subset of notes, and then progress to the full scale.
I have another ear trainer that has lower levels where you first only identify CDEFG, then full Cmaj scale, THEN full chromatic scale, which is great for beginners.
The Perfect Pitch app is nice if youre more advanced but jumping in to trying to identify the full chromatic scale with no background is challenging.
The other obvious problem is, as another reviewer mentioned, youre really relying on relative pitch recognition. After I spent some time with interval recognition on another app, this one was suddenly really easy.
The pros are: simple, attractive, easy to use, and really nice sound quality. I find the keyboard sufficiently large to tap the correct keys reliably. And, well, its FREE! Im definitely keeping it in my ear training arsenal for periodic use.
I hope the developer will make some more improvements to support different levels (novice to experienced), and recognition of notes at higher and lower octaves (jumping around might discourage easy relying on interval recognition). If that comes out as a paid app Ill definitely buy it!