Jamboo / Nicnac,
I collect my new IS250 from the dealer this afternoon. After I took a good look around inside and out, he told me the inspection guys had taken it for a very good spin (30km!) to look for the rattles I had previously told him were being reported by numerous people. He said they found none. I didn't have time at that stage to take it for a drive myself before taking delivery.
On my long drive home (motorway, and bumper-to-bumper stop/start), I didn't hear one rattle or any wind noise. In fact, the car is extremely quiet. It is significantly quieter than my previous IS200. It is a different car entirely.
At one stage, I thought I did hear a very minor rattle, until I figured out it was a stratch on the classical music track they were playing on the radio!
So, all is not lost! Let's hope no rattles develop, as has also been reported here.