I run the MT SS 275/60 at 30psi and dont notice any swaying at all on the highway. They also hook very well on the street at 30psi. I don't have any experience in the rain with them, but I would imagine they would need to be driven carefully especially if there is any standing water on the road.
Im running the 295/55/15 S/S and the only thing I notice is vibration which is the same with all the other drag radials I've had. No sway or anything else though. Grip is nuts.