I put 444s and monotubes on my bike ('12 FLHTK) back in November, and can only say that it is a different bike altogether.
I specifically went with HD springs since I ride with the wife quite a bit, and when solo I like the extra firmness. That extra stiffness is not for all, to be sure, but it works well for me.
"Yeah, that'd be funny...if I was stupid."
"Others laugh at straights who laugh at freaks who laugh at squares...."
- Kris Kristofferson, "Jesus Was A Capricorn"
'12 FLHTK Ultra Limited, Vivid Black, Stage II (Rush True Duals and Slip Ons, SE-204 cams, SE/K&N AC, PCV, SE Push Rods & Lifters), Progressive Monotubes and 444s, SLAYER blasting on the stereo!