Getting 100% comfortable takes me some time. I'm one of those people that prefers to feel out the entire bike so I know my limits etc....After riding the 500 around for so long the f4i will keep me happy for a LOOOOONG time. The Ninja was easier to get comfortable on of course. Sucks not being able to put my feet flat on the ground on the f4i but a dogbone might be in my future. I don't think I'll ever get sick of the 600 nor will I ever feel the need for a 1000.