I've been using inline roller skates as my primary mode of transportation for the past month. The city I am currently in was clearly not designed for bike or skate traffic, but some newer areas are more accommodating. I've managed to do anything I would have used a car for, on skates. It certainly requires more logistical creativity, but it's a much more enjoyable experience and has no adverse environmental effects.

I would be thrilled to participate in an Elfstedentocht. I am somewhat trained and have my own figure skates, though I'd want speed skates for this event. The 200km seems doable, especially since there would be no elevation changes.