This is one of the most original compositional styles I've heard in a long time. The song lacks a traditional melody, yet it retains my attention for the entire duration of over four minutes! The piano layering is magnificent. I love how the low frequencies act like a pad, supporting the higher notes.
My only complaint is that I think the mix seems to be a little flat; it could sound airier. But I do understand that applying this effect could be extremely difficult considering that the low frequencies already sound spacious.