I find that if I have the drawing tool active and type command-z, rather than undo the last draw operation I did, it undoes the last operation I performed with the previous tool (e.g. the last move or re-size I did with a select tool).
This is rather irritating even when documented, because it means that if I make a mistake drawing I have to activate the "select drawing" tool, select, backspace, select the "draw" tool, reset the colour I was using, and re-set the line weight I was using: six operations instead of one with a working "undo".
