Interesting thread, I haven't read it all but I have an LS460. It's had a few minor issues but absolutely nothing remotely expensive. Only had it since November 2019 and it hasn't let me down (yet!). I read about the gearbox/radiator problem and had a new OEM radiator fitted out of precaution. Other than that, and general servicing I have had to replace 1 wheel bearing and I had to get the ride height sensors removed and thoroughly cleaned because at times the car was a bit "wonky" with its ride height, but that is now resolved and didn't require new parts.
Overall it has been a very good car. There is always a risk of bigger bills with more complex cars, but the additional performance over an LS400 is very significant, coupled with (slightly) better economy and more creature comforts available (especially now I have a GROM unit fitted - I have full Android integration) means that, for me, those risks are worth it. The way I see it, I bought the car outright, it isn't really depreciating, and the monthly payments on a new car lease deal would easily pay for any unexpected servicing costs on the LS460, and I am driving an LS460 instead of some dreary 1.4L diesel hatchback or whatever.