I own a motorcycle shop that works on pretty much nothing but harleys, I have four full time master certified harley techs doing the wrenching. They have done service, tire changes etc on my spyder and absolutely love taking turns riding it. I ride with pretty much all harley's and the funny thing is those guys will spend 10k building "performance" motors (which is good for business) but at the end of the day if you want to go fast go buy a $10k hayabusa and be done with it.
I can have mutual respect for all forms of motorcycles for what they are.
I will say after racing countless screaming eagle street-glides, road-glides, big bore softails, etc I have yet to find one that was able to beat my spyder stop light to stop light back when it only had a hindle. The only harley to ever "smoke" me was my friends v-rod muscle, since I put a turbo on the spyder those tables were turned and I can put a couple bike lengths on him by 100mph.
But as I said before, if you want to go fast save yourself the time and money and go by a 7-10k sport bike that runs 9s-10s bone stock. Speed is relative and the spyder will never be what I consider "fast", even with 250hp it will never have the traction needed to be seriously fast.