I played D4DJ and here are my thoughts!
I think that it will be a good game when the whole game is released! The gameplay is similar to bandori but harder imo. This game wasn't made for phone screens and thumbs (what I use for bandori) and I won't get the whole game when JP releases. If an EN translation appeared, maybe I will. Just not on my phone.
The songs are all good, my favourite being Flash Movement. The pink slider thing is probably the worst bit but that's just because I was on a phone.