The 1UZ has a reputation for reliability for a reason, I think.
I don't remember where I read this, (Maybe SF?) but some posted a story recently that went like so...
There's a machinist who does all kinds of work. He's seen about every type of motor come into his shop with a variety of problems. When asked what kind of car he would buy if he was on the market, he said a lexus (ls430 or something like that,) based on the fact that he'd never seen a broken motor come through.
That's in line with every other thing I've heard about it, as far as reliability.
It may largely be hype, and it's obviously not going to last forever under boost. It's not magical, but I do have a lot of trust in the engineering that went into it.
In the end, though, it's just personal preference. You could say the same thing to MKIV guys, about putting LS motors in place of their 2JZ's.