Having now created a significant # of desktop drill-down reports in just a few weeks, I am now ready to view the same on an Ipad.
One suggestion to help in this scenario (and also on the desktop rendering if a small screen) is for the Drilldown Menu Icon to appear on the left instead of the right (while still creating a popup selector of child reports).
Browser rendering on all devices always preserves the left hand columns whereas the right-hand columns may not be in viewable at all on the Ipad and only with slider bars on the Desktop