I have all three devices and here is my take:
Android sucks - Nothing great. Interface is cheap. It gained popularity because every mom and pop device manufacturer started making cheap android tablets. It's lying somewhere in the corner and I don't bother much.
iOS - Nothing new. I am tired of the same interface. I still spend couple of hours per week for casual surfing and playing free games. I haven't done anything productive using iPad. It is kind of nice to have but I can still live without it.
Win8 - I just love it. New look, new design and way different and much more advanced compared to others.