The new diff functionality in dokuwiki-latest (as of today - March 5, 2008) seems to have a bug:
You can select more than two revisions with the new diff checkboxes, but the diff output will only show the diff of the two most recent revisions that were selected. Users should probably only be able to select two revisions to diff (for example with radio buttons, like the diff patches located at
http://wiki.splitbrain.org/wiki:discussion:diff ).