It would be helpful if delimiters for the various operators with list capabilities were standardized to one character. Using spaces doesn't allow you to search on items with spaces in them (perhaps using single quotes?).
Also it's a total guess as to what delimiters should be used with which operators currently. For instance "contains any of" is a space delimiter while "equals any of" is a comma. The only reason I know is because Jen Lasser told me (and even she wasn't sure if "contains" could take commas).
There should be an indication of which delimiter is required when an operator is selected. It's a simple text addition and would avoid a good deal of trial and error.