The one thing you will immediately notice is that a new bike "feels" faster, jumps quicker. Look at the numbers over a 40 mile ride and you will find the real difference in speed is negligible if any at all. Upgrade the bike with light weight wheels and you will notice the thing will jump quicker and climb a litter easier, if your physical condition is able to push things a bit. Other than that, nope, a new bike will not gain much in performance at this point.