Wanted to say thanks to JPI for his real world experience with the oil sludge issue. Really helpful.
For all those people who want to change their oil around the 7.5k - 11k area, what's the risk /reward ratio here? Let's say you drive 25k year (~70mi/day), a lot I think for most, you change your oil at a $20-$50 oil shop every 3k, so you're looking at 8 times x $50 = $400 a year. You go the 5k or 7.5k route outlined in the manual, you're looking at 5 x $50 = $250 or 3 x $50 = $150. You save at best a few hundred -- but you are driving a Lexus, not a Geo.
Compare these savings to proving your point in court against the manufacturer is dicey. Not an expert here, but having just a few cases where you take the oil up to 7.5k - 11k, does not help your case, especially if you've received a letter from Toyota or have gone to the dealership, where I'm sure they'll inform you.
So what is the point of experimenting on this car? If you want to test oil reliability then buy a cheap beater car and test it on that. But in any case, 1000's of cases from mechanics and the manufacturer vs a small sample size of users with success at 7.5k - 11k oil change intervals does not sway me -- it sounds too much like the "flourine in the water is pointless" or "regular dentist checkups are a waste" arguments.