Are the early Ultras that much different from the new ones ? I've had mine for 4 years and never once wanted to change anything , except the throttle , which I removed immediately .
That's why I like my long wheelbase bike with 3.5" tires. Not the quickest handling but very stable on our crappy streets. I get real antsy when I demo new bikes with narrower tires and shorter wheelbases.
I would not ride a bike on the street with knobbies. I crested a hill on a new trail and there was a washout with 4 to 5 inches of sand across the path. It would have been ugly with skinny tires at close to 30 MPH. YMMV