I have heard several people talk about a condition that the IS300 exhibits occasionally. It is described as a rough shift that is to be fixed by the ECU update. Many articles have pointed out something that sound just like this regarding other vehicles that Toyota/Lexus make, the Camry, Solara and ES300 (all of which use the 1MZ-FE engine family). I personally drive a 95 V6 Camry; before I changed to a synthetic transmission fluid it would occasionally do this. It usually happens during a shift from 2nd to 3rd. The tranny free spools for a second then slams into gear, "just as the other articles state". It has not done it since the synthetic fluid (Mobil 1) was put in. I just wanted to write this because it appears this is not a new problem belonging only to the IS.