I have never taken a photo on my phone and then found the need to instantly print it. Besides, it takes 10 seconds to get it from phone to PC then print, so I could never justify buying one, seems like a waste of money to me.
That said, I am impressed at it'a tiny size. and the fact that it doesn't require ink. Bottom line is though, if you really do need to print your photos instantly, get a normal Polaroid.