I’m surprised to not see this one at the top of the list… Opening character sheets is painfully slow, and as a GM of a mid-level (13th) Pathfinder game I’m doing it constantly. Changing auras, adjusting icons, checking abilities, I’m regularly referencing the sheets. I have a decently fast computer and gigabit internet and it still takes a minimum of 4 seconds to open a character sheet (blank window for about ~1 second, then ~3 more seconds of unusability while it tries to load the PDF), even if there’s no PDF and no actions associated with that character. It should be nearly instantaneous to at least open the window and start working, even if we have to wait if we want to do something specifically related to the PDF/image.
Yes, I could open each one in a window and leave it open but I have a party of 7 and potentially that many more enemies as well so I don’t think it’s really going to be faster for me to dig through 14 windows to find the one that I want to make changes to.