All posts above are correct. Yes, better the devil you know, but the only thing that really changed between old and new is plastics (engine and chassis are pretty much the same). So, it's a bit of a spend to upgrade the whole bike, but understand that it's ten years newer (at least it was for me).
Plus, you get to enjoy the fruits of another's labor (thanks for the suspension, Steve!
), and you get a chassis with that many less hours/miles. A new platform on which to begin your next journey.
I wasn't disappointed in the least, everything is close enough that the pluses outweigh any negatives (of which you will discover with any purchase or rebuild). Negative: Lost the U Rims. Plus: Lost ten lbs (it feels!) with the Excel rims. And so on.
The evolution in suspension alone is worth the change, in my opinion. However, I don't know squat about suspension adjustment, so getting something properly set makes it worthwhile to me.