First of all, thanks to this forum for providing a ton of information as I was deciding what kind of bike to buy. I have had RC51 on my brain for at least a couple of years, and was considering a few other types, but finally decided to pull the trigger on the RC last month because they're awesome and you don't see them every day. I hadn't owned a street bike since a pretty bad accident in '98, and have been riding and racing dirt bikes over the past four or so years, so I finally sold one of my dirt bikes and found a super clean and bone stock '04 RC51 with 18k miles on it. No idea about the owner history... probably at least a few, but it's definitely in really good shape. Going through it now with air filters, plugs, coolant flush, and a general inspection of everything I can get to. It had just had an oil change before I picked it up (for a really decent price).
I've already molested it a bit with an undertail kit (Bestem), Proton blinkers up front, some brand new Two Brothers aluminum slip-ons, a PCV, and some nice new BT016 tires. I also recovered the stock seat with a nicer cover, and got some braided brake lines that I'll get around to installing at some point. I did all that in the first two weeks of ownership and have no regrets! The only other thing I really see myself doing to it is the 15-41 gearing swap (and 520 conversion).
I am extremely stoked to have this bike and I'm blown away at how nice it is to ride, how great it feels in the turns, and how awesome the v-twin is in general...it definitely gets some looks with those pipes making such an incredible racket!