Never used the Trash icon either (and generally don't show the Toolbar). But at least the Tooltip is correct:
Now that I think on it, clicking "Trash" _should_ put the item in the Aperture Trash. The confusion comes from the use of "Delete" -- specifically using a key with that label to execute a command that changes based on not only what kind of item is selected, but where the item is located. So in this case (let me parenthetically add I have yet to take part in my morning caffeine ritual) "Delete" in the Tooltip does not equal "press and release the 'delete' key", but rather is used as a verb (rightly, imho).
Not sure what a better design might be, but perhaps at least popping up a window saying, "The selected items are Images in an Album. Would you like to remove them from the Album, or move them to the Aperture Trash (which will delete them from the Project they are in)?".
Greg -- I suggest using the context-sensitive menu (a/k/a "right-click") to select the command you want:
Message was edited by: Kirby Krieger - formatting and clean-up.