I have a speedmaster and i put a set of progressive 440's on it 3 years ago. Not only did it eliminate 80% of the back crunching jolts from potholes, but the bike handles big time. I mean, it always handled good especially for a cruiser. But i've ridden with a couple bonnie guys that ride REAL fast in the twisties and they were both very surprised at the fact i stuck to them like glue. I gotta tell ya, i am prone to ride the twisties a bit hard at times, but these guys had me taking the speedy to speeds i'd never usually do. Foolish of me to even follow them i suppose, but it sure was a surprise to me too just how this *cruiser* handles. and i attribute a lot of that to my suspension which is progressive springs up front and those awesome 440's on back. if you really want to the best for you bike get some progressive suspension or at least some other good quality shocks with a good rep. Your bike will feel better, but when you really push it is where you will see it's worth every penny. Like Carl said tho, if you just put around sedately you won't notice much except potholes aren't as bad. I've had this bike close to triple digits in twisties that i'd normally stay under 60 mph in, and not even a bit of wobble or anything....just tracking like it's on rails with a confident feel no other bike i've ever had was capable of.
