the fuzzy coats on the HBWR contain cyanogenic glycosides (=apple seeds)
the embryo contains a soap-like substance that will make you nauseus (passes in 2 hours or so) the shells contain a more toxic compound that is really unpleasant - so dont grate the shell too much, then strain and discard. (the actives you want are in the embryo, mixed in with the nauseas soapy stuff)
so 3 things to worry about! - the worst 2 you can mostly eliminate quite easily by coarsely grinding/soaking/straining but the nausea youll probably have to put up with (unless your prepared to do some chemistry)
How do other seeds (eg. morning glory) compare to HBWR. I heard they were more LSD like, but mainstream suppliers coat them with poison.