Relations with multiple members like http://www.openstreetmap.org/?lat=57.011&lon=-6.428&zoom=10&layers=M are rendered multiple times and are a bit of a cartographic disaster.

One possible fix is to import with osm2pgsql in -G mode to create a MULTIPOLYGON instead of multiple POLYGONs. @springmeyer informs me that mapnik should render the label on just the largest POLYGON within the MULTIPOLYGON by default.

Do we know anyone running with -G?