The issues I have experienced with touch screens are similar to those encountered when using iPads (there are iPad Best practices information on Qlik Community).
Typically issues I have come across which is not an exhaustive list include:
Decide on portrait or landscape mode - don't vary as this is annoying.
Make sure everything fits on the page available to avoid scrolling.
Mouse-over chart functionality doesn't work.
Scroll bars may also not work properly depending on the device but if they do, make them chunky for users with fat fingers . This may apply to other features as users easily despair of icons and actions are not easy to navigate by touch.