I was all set to put one on a build until I had a conversation with a gunsmith about trying two of them on his own personal rifle. He went through two and both had the same problem with coppering up real bad so I kind of cooled on the idea of using a barrel that cost twice as much and potentially wouldn't turn out well. Ended up with a tried and true #4 Hart instead.
But, I have to admit, I haven't completely soured on the idea of using a carbon wrapped barrel on a build and have been seriously kicking around the idea of going with a Hardy Carbon Wrapped barrel as I've heard good things about them.
For me, they definitely have a pleasing look to them and when used with a muzzle brake of the same diameter as the barrel, they just "look" better but in all honesty, short of having a certain "cool" factor or being more pleasing to the eye, I don't know that they offer much over a steel barrel, but, having said all that, I still want a build with one. Just not sure which one I want to take a chance with because the thought of spending double for a barrel and having it not turn out well, is a concern.