Welcome to the lunatic asylum!
Mine will cruise easily at 80 all day,although it's a little buzzy,mainly due to the tires.It's not a Lead Wing, so it really depends on what your requirements are.Smoothness is just a tire change,and a little bump in gearing away.
I've got to be honest with you.If all day highway cruising is your forte,you might want to look elsewhere.The Scramblers bag is twisty backroads,and relatively smooth dirt trails.Looking cooler than anybody else while cruising the boulevard is just a bonus!
If you use your Scrambler the way Scratcher and I do,which is pretty much only staying on the tarmac until we get to the dirt,the Scramby will be a fair dinkum ride for you.(Did I say that right,Scratch?)
Plastic parts include head light & tail light assemblies,turn signals,side covers,mud guards,and seat pan.I think that covers it.Oh,I guess the '08 models also have plastic tank badges.I personally don't have a problem with this.Back in the days when the original scramblers were being built,we all used to junk our steel parts,and go out and spend big bucks to get plastic or fibreglass parts for our bikes,in an effort to reduce weight.Here the factory has done it for us.They should be applauded.

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Again,welcome.I hope you love your Scrambler as much as I love mine.

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Cheers!
Bruce