Charts cause a HUGE problem for us left-handed knitters...I don't think many designers appreciate this when they do not also offer written instructions.
If I'm following written instructions, that's fine, my finished item just turns out a mirror image of what a right hander would do. Its more complicated when following charts as I need to work out whether the cables and increases/decreases will go the right way and re-write these before I start.
....don't even get me started on what happens when part of the pattern is written instructions and then refers to a chart!!!!