Bill, I have nothin' but praise for the carbon fiber rods. Before getting this PS acoustic, I had the early Tonare Grand Artist model, and it came with a carbon fiber truss rod, too. It also stayed perfectly stable.
In fact, I can take my acoustic out of the case after not playing it for weeks, and it's still nearly perfectly in tune, which you have to admit is pretty unusual for an acoustic guitar - though I do use the D'Addario humidipaks, which probably helps a bit.
I've noticed another great thing about these guitars with carbon fiber rods: the guitars sound very "woody", the way old Martins used to before they went to adjustable rods and only had a T-bar. I would guess it might be that the less metal inside the neck the better. Carbon fiber would have a very different "resonant ring" from metal. However, I admit it may not be a factor and the guitars might just be woody sounding for other reasons.
I suppose one never knows for sure with this stuff, but no adjustments of any kind since I got the guitar in 2013? Seems like a good track record.
I just re-read my statement that I can go weeks without playing it, and now I feel guilty that I'm not giving the guitar enough love!!