I have been using 452X for a good while now and have no reason to go away from it.
I know of two string sets that Gas is replacing that were using the Ghost material. After already replacing once they are going to 452X. The owners were constantly twisting them up, I know at one point a TRX 40 took 12 twists in the string to get it back to spec. I do know a lot of people using gas, so it might not be a huge percentage. I think generally they build a good string, been wondering if they had a bad run of their ghost material.
I wouldn't leave a material unless you have good reason to. 452X has served me well, maybe something else out there is better, but I don't need to be the guinea pig. I think Bcy will say that the Mercury is more likely to stretch than 452x. X-99 is interesting, but again, I'll stay with what I know is working for me.