"File Open" doesnt work (no way to choose a file, only directory possible), but you can get around this by choosing file in the window. The windows version is far better (no quirks)
I like it very much and use it often :) A pity there is no way to edit files or open blank comparision, that's why I sometimes use Meld instead.
there's also a stripped-down version called kdiff3-qt not depending on the kde libraries , better.
Also works under gnome not just KDE