Ive had a few xs's with firestones on them. I dont drag my knees or do many high speed blasts... but I ride about 10-15k miles a season. I have a few vintage bikes, and a few more modern bikes. So if i want a modern tire with better performance I just ride a different bike...
They will squirm some on veins in the road, but never really had much of a problem in smooth turns with them... That being said they are pretty much a fashion accessory... way too expensive for what they are... but even with every damn build in the world using them, I still think they look pretty cool...
my .02$