Pro Keyboard is awesome! Very happy now. Sure, there are some early 'warmup' level songs where you think - why does this track even have keyboard in it in the first place, where it is just some nonsense synth that barely adds anything and is drowned out completely by bass and guitar, but as soon as you get to difficulty levels of 2 and up, things start to get pretty exciting and there is some great music to be played.
I am also quite pleased iwth the keyboard lessons in the game - I never took actual lessons and although I can find my way around the keyboard fairly well, these lessons are actually useful. I could get through the advanced scales lessons for instance pretty easily, but they did teach me (and in one case reminded me) the correct way to do various scales with helpful pointers about what technique to use which was in part why I managed to do them so easily. By contrast, some of the advanced chord lessons took me an hour to get.
The major downside I guess would be that the game basically only teaches you one handed play, so if you want to progress beyond that you'll need to either teach yourself to play basslines with your right hand, or get real piano lessons. But I'm having a blast, and when I played some freestyle after my long session (I think I may have played 4-5 hours straight), I was already a better player.
I had a tonne of fun with a song that has some really jazzy chords and progressions. It is very hard (even if it only says level 3 or so) and I went into training mode for it to learn the chord progressions, and am quite a bit from mastering that song yet, but it is a really great song. Can't find or remember the title, ironically, but it was very late. Will look it up.
It's probably a DLC song, come to think of it.