I find myself using categories more and more. I have to admit I use them mostly like tags, so that they are by no mean exclusive. For instance, a contact could be part of “Friends” and “France” as two independent categories.
Would it be possible to select multiple categories in the main view using e.g. CTRL, and view the combined list of contacts? In this case, by “combined” I really mean the intersection of both (or more) categories, so that clicking on “Friends” and “France” while holding CTRL down would select my friends from France, but not from other places, and not those people that are not my friends (the equivalent of a logical AND).
Alternatively, selecting categories while holding SHIFT down would select all contacts that are part of any selected category, so that in my example, I would have all my friends and every people from France together (the equivalent of a logical OR).
Ideally, the two alternatives (AND/OR) would have the categories in the left column colored differently. It’s currently blue for any selection (but I wonder if it’s theme/system specific), could be for instance some green for AND and reddish for OR…