The trains in the Netherlands are very frequent but there are some pitfalls for foreigners. First and most importantly - there are rules posted in Dutch and in English but when they post amendments to those rules (like they did 1 October 2005) they only post the amendments in Dutch. Thus, don't believe what you read in English. The key piece of information I was missing was that it is no longer possible to buy tickets for a higher rate on the train itself. Indeed my ticket man laughed and said they don't sell tickets, they only sell fines. The fine is 35 Euros. The reason I didn't have a ticket is that the ticket windows are all shut down in the small towns I went to (and carry a 1 Euro transaction fee in the large towns which have them) and so everyone must use a ticket dispensing machine. The Dutch train company is worried that if their machines take bills they will become a target for vandals so the machines take coins and bank cards. The bank cards only work if they are Dutch. My international cards, my French cards, nothing worked. Turns out those cards work at the airport and no where else (seems like a trick to me!). I was reduced to trying to buy things to get coinage as change (the banks, when they are open, charge to give you coins) so that I could get 36 Euros for a round-trip ticket to Amsterdam. I didn't manage to get thirty-six coins, which is how I found out about the rules for buying tickets having been amended.
I later saw that it could be possible for a foreigner to get some kind of travel pass before arriving - much better!