It's a shame... mostly because there's no wealth of information about them on the net, like the KDX has. This bike deserved a stronger following. It's not the best looking bike out there, but once you put a sticker kit on it and replace some of the dated looking ADR gear with acerbis stuff, they look nice.
I've seen some pictures of US RMX's on the net, and they seem to come with a huge muffler / spark arrestor. I imagine that would have killed power big time. We got a smaller MX style muffler, which works ok. Some people cut open the expansion chamber and remove sound deadening for a bit more punch.
I think the WR's were critized for being a bit savage to ride. I mean they're were basically a YZ, with a flywheel weight and a wide ratio gearbox, probably a few other things too, but nothing major. Would annihilate any new wr250f in a straight line though :p