The motor isn't made by HD as someone said earlier, they're made by Rotax.
I haven't ridden a 1125R, but the other Buells I've ridden have shifted like total dog shit. Granted, the 1125R has a slipper clutch, so maybe it's different.
It will vibrate your teeth out, it won't go around a track as fast as a normal sport bike, the front end is horridly ugly, they have complaints about heat on the right side and they're well, built by Buell. Not a fan.
That said, if you buy one, let me ride it. I'll tell you what I think then.