In default view orientation x-y-z (as below picture), it is normal. i can change viewpoints easily by mouse (that is, when the mouse moves up & down, then the model rolls up & down; when the mouse moves left & right, the model can roll left & right)
However, if the view orientation is changed by 90deg (say y-z-x), i find it is very hard to manipulate viewpoint by the mouse. (in this case, when the mouse moves left & right, the model rotates CW & CCW.)
i don’t know whether it happens in ipad version too (Tried, same problem). i think that view manipulation should not be binded to xyz datum.