I've used Castrol Edge 0W-30 for the past three oil changes on my LS430 and I'm very impressed. You notice it most when you start it from cold. With the oil that Lexus use, when started it would rev to about 1,400 rpm then settle down to 1,000 rpm. With Castrol Edge it now revs to 2,000 rpm when started. My mpg has also been slightly better by 2-3 mpg as well. Looking down the oil filler tube, it has also cleaned up the inside of the engine as well. When I first looked down it when I first bought it, the inside was slightly brown. I looked down it after a year of using Castrol Edge and it now looks almost silver and new. I can't recomend it enough. I'm going to start using it in my Nissan Micra driving school car.
It's probably overkill but I do change the oil in the Lexus every six months. It doesn't do 10,000 miles per year though but it makes me feel better.
Jim.