Well, I've put about 1500 miles on my (new to me) 2009 SERG after converting to Bitubo rears and Traxxion fronts. Chalk up one more believer – this is money well spent. I weigh about 240 lbs and usually carry 30 lbs of stuff on the bike. I usually ride solo, often on chip seal roads in Texas Hill Country. Hill Country roads offer numerous gentle and moderate curves, but are often improperly banked and frequently have washboard texture. If you're too young to know what a washboard is, I'm sorry, but that's the best term I know to describe the surface.
I returned from a very nice rally this weekend at TX Sate HOG in Wichita Falls. I have ridden all types of roads and surfaces since the upgrade. If you weigh 175 lbs, never carry gear or ride two-up, always ride cautiously, never brake while using the throttle or while leaned over, then you might be happy with your stock H-D suspension. Otherwise, you know how wimpy stock is.
Suspension feel is obviously very subjective. I just sold a 2010 Ultra Classic with 10.000 miles riding on Progressive 440 heavy duty rears and the Progressive fork upgrade in the front. While this as definitely a big improvement over stock, I'd rate it as moving from 2 to 5 on a scale of 10. Bitubo and Traxxion is the 10 for me. The bike is planted, stable, and very predictable.
I rode two up for part of the rally. This is something I've generally avoided, because my wife usually rides her own and riding two up previously felt like riding a lumbering elephant with weak knees. Not anymore – other than parking lot speeds. Above 5 – 7 mph, this bike handled very similar to the way it rides without a passenger. My wife's decision to give up riding is going to be much easier now that I have this suspension setup.
I had the work done at Raceworx in Alvarado, TX. Hat's off to Jim Cambora for doing a super job for me.