I ran the T1R in 205/55R15 and 225/50R15 on 15x6.5+45 wheels for many years. When they were new I got the same experience as others. They felt a little slippery and floaty for the first ~1000km. The tread design is definitely going to move around with steering input at full tread depth.
The side walls are quite soft. When the tyres are off the wheel you can move the side walls quite easily compared to some other performance tyres. Direction changes with these tyres is quite delayed and especially going from fully loading the tyres in one direction to fully loading in the other it's quite an unsettling experience. You know the tyres will grip up but the feeling you get in between the transition is not confidence inspiring. I've now gone to RE003 in 215/40R17 and 245/40R17 on 17x8+37 and 17x9+29 and the handling difference is huge. Very direct and on demand where you want the car to go and when. Sure the ride is stiffer due to much less tyre but I prefer these over the T1R.