The chassis should be pretty night and day from your 2003. People with the F53 Ford with the 6spd report some pretty major improvements over the older ones. More gears = better hill climbing at lower RPMs. Also, better soundproofing in the cab on recent coaches for an overall better experience.
Lots of discussion on people wanting/needing suspension and steering improvements on a stock F53. So, don't get too discouraged if this one doesn't handle perfectly right now. It may or may not be different from your 03. Also, you may have just gotten use to the behaviors of your 03 so you'll have a new learning curve. I've always figured if I get a new/newer F53 I'd budget a few thousand dollars to some suspension and steering upgrades - steering stabilizers, anti-sway bars, beefier springs, etc.
As for the inside of the coach, 15 years is a lifetime of wear and tear so you should be in for a pretty nice upgrade. I REALLY like the drop down over cab bunks on these newer class A coaches. Congratulations and have fun!!
