It's valid on international trains going through Holland, with some exceptions, make sure to check those out. Also, the bike ticket is not valid during rush hour. I tried to find a link on the Dutch Railways site (
www.ns.nl) to the bike ticket in English, but couldn't find it, eventhough the site is available in English. The ticket is called 'dagkaart fiets' which roughly translates to 'bicycle 1 day ticket'.
I rode fixed in Amsterdam a few weeks ago and it was utter chaos! I really had to be careful not to be run over, but then I'm not used to really busy traffic. But I guess u were referring to the general bike friendliness of Holland, because of the millions of miles of cycling lanes. Oh yeah, if you ride in Amsterdam, or Rotterdam or any other citu that runs trams, do not get your wheel jammed in one of the rails, that would so suck!
Cheers