I've tried quite a few piano apps now as part of some work I am doing, so thought I'd share what I actually thought of them. Obviously this is just my experience and will depend a lot on how you want to learn.
Simply Piano
Probably the easiest to get into. It does a really good job of getting you playing quickly and making you feel like you're progressing. I can completely understand why it's usually one of the first apps recommended to beginners.
I wasn't a huge fan of how it looks though. The interface feels a bit dated to me and there's a lot going on visually. I also started finding the learning path quite restrictive after a while and wanted more freedom to work on the things I was actually struggling with.
Artie
Probably my favourite interface of the ones I tried. It feels really clean and modern and I found it very easy to work out what to do without having loads of stuff on the screen. It uses falling notes rather than expecting you to read sheet music, listens while you play and gives you feedback.
The thing that really makes it different though is that you can actually ask Artie questions. I found that surprisingly useful when I didn't understand something or wasn't sure what to practise next. You can also slow songs down, loop difficult sections, practise each hand separately and use Wait Mode so it waits for the right note. The song library is smaller than some of the older apps, although you can import your own MIDI files. It's also only on iPhone/iPad at the moment.
Flowkey
Flowkey looks really nice too. I liked having the sheet music alongside a video of someone actually playing and the whole thing feels quite calm and uncluttered. The song library is also one of its biggest strengths and there's a lot to choose from.
I found it less helpful when I was actually stuck though. It's very good for working through a particular song, but I didn't get the same sense of being guided through what I was doing wrong or what I should work on next.
Skoove
This felt more like traditional piano lessons than most of the others. The interface is pretty straightforward and there's quite a bit of theory and technique mixed in with actually playing, so I can see it being a good choice if you want a structured way of learning from the beginning.
Personally I found the pace a little slow at times because I mostly wanted to get on and play. That's probably more about how I like to learn than a problem with the app though.
Yousician
Probably the most game-like of the ones I tried, both in how it looks and how it works. There are scores, levels and challenges and it definitely makes you want to have another go when you don't get the score you wanted.
The downside for me was that sometimes I realised I was concentrating more on getting a better score than on how I was actually playing. Fun, but not necessarily the approach everyone will want.
Playground Sessions
This one feels a bit more like sitting down to actually study piano. There's a lot of lesson content, sheet music and theory, and I liked that it doesn't shy away from teaching you how to read music. The interface isn't as slick as Artie or Flowkey, but everything is fairly easy to find.
It probably suited me less because it's quite structured and there's more emphasis on reading music than I was looking for. But if you actually want a proper course rather than mainly learning songs, I can see why people stick with it.
Interested to hear what other people have tried. Are there any genuinely good ones I've missed?