I think it's important, at least for now, to view this in the context of a luxury vehicle, not a track car or enthusiast car.
The lag is the biggest issue by far, but also something most people probably won't notice, and also something that can probably be solved without much issue. Infiniti already did steer by wire with adaptive ratio. It was a bit numb when first launched but is pretty snappy these days. The rest of the Lexus system seems sound. I think potential lack of redundancy is a non-issue as long as the failure mode is safe. Mechanical systems will almost always give more redudancy, but if the failure mode can be controlled then that redundancy just becomes a point of convenience for a non-standard use case. Most people will never know.
There's certainly going to be a learning curve but just going in with the understanding that you aren't going to have to make any hand over hand movements, most people should adapt pretty quickly. Think about how quickly you can adapt moving between different vehicles. You might not like the difference, but you adapt quickly. Day to day steering is mostly micro corrections. If this smooths it out then most people won't notice. This is also being implemented with whatever other lane assist and collision prevention features the car has.
That said, as cool as I think this is from an engineering perspective, I won't buy one.