I can't comment on the Yamaha, but my 204 SC has worked well, although I only have 10 hours on it. I did have to replace the battery after 2 years (I now keep a slow charger on it during the "off" season) and the starter solenoid at the same time. The dealer did a spring checkup but didn't channge the plugs so I had a problem with power at the start of last season. As soon as the plugs were changed, it worked fine - for the whole season.
Overall, I think the Ski is fine. As to the washer issue - I guess there must be a problem, but I haven't had any problems and no has anyone else in the marina I moor my Sea Doo in.
This year I am trading for an RXT X, that comes standard with metal washers. if the washers are you major concern, you can have them changed to metal and not have to worry about it.
I'm not sure what happens when the washers "go", but some have posted that the parts can get into the oil. If this is the case, by the time you limped home, the engine might be "toast" as well.
I'd check with the Yamaha owners to see what issues that ski has.
grover