Hey Craig...
Well from my experience, I would really try to get a 2007 or later. If you're patient, you should be able to find a 2007 for a pretty good price. Now I have talked to several people that own '04's and '05's and they love them, but I would really try to get an '06 if you're looking to get an older one. I have read several professional reviews that talk about fuel injection issues on the '04's and sometimes '05's (again, lots of people here have them and rarely do I hear about any problems). I have an '06 and an '07. The '07 is just a much better design IMO. I can definitely tell a difference when I go back and forth and ride them both. DefyInertia listed the major changes but they also added a better instrument cluster and a helmet lock lol. I sometimes have a hard time reading the digital tack in the sunlight on my '06 and prefer the analog needle tack on the '07 much more. From what I've seen, there is a much wider support for aftermarket windscreens on the '07's and up.
I bought my '06 with 18,000 miles on it... rides perfectly. These bikes are very well made... built much better than lots of the others out there. As long as the bike was taken care of, I wouldn't worry about the miles very much. The only thing you may have to worry about is replacing tires, etc.
So bottom line, if it were me, I would buy an '07 (the biggest bang for your buck)... and maybe settle for an '06. And by the way, the FZ6 is such a great motorcycle! I have yet to meet someone that has been dissatisfied or disappointed with it.
Hope this helps! :thumbup: