at least, as long as we don't have to start worrying about the ethics of what it might do if it encounters aliens.

Well, that is quite horriffic. Poor non-humanlike alien minds...

I don't think the SH's plan was anything like Huxley's BNW (which is about numbing people into docility). Saying pain should be maintained reminds me of that analogy Yudkowsky made about a world where people get truncheoned in the head daily, can't help it, keep making up reasons why getting truncheoned is full of benefits, but, if you ask someone outside of that culture if they want to start getting truncheoned in exchange for all those wonderful benefits...