Congradulations. I'm just like you, going from a FXDS to a RKC. Night and Day is the only way I can discribe the differnece on the freeway. Everybody here complains about the stock handle bars. I will say, I didn't think I liked them at first, but now after a few thousand miles....they feel just fine to me, and I do not plan on a change. I trimmed off about an inch and a half off the top of the windshield, and added front fork air deflectors....fits me like a glove now. Good luck with yours.
Thats the classic New Bike grin if I've ever seen it! You're gonna love it, and you'd better because you're going to dump a ton more money into it. WOOT!