I almost always want to measure in feet and acres, but the tool defaults to metric units. This means I have to change the units every time I open the tool.
this is still an issue at 3.3.1. Defaults to Imperial (instead of US Feet), and does not save between map tabs or saved sessions in the same project.
I'll add that this would be really helpful. We have a lot of staff that need quick measurements and it seems like one should be able to choose defaults for these. Also, it would be nice to be able to set the default for the mode.