Even if we accept that creating conscious entities which are forced by means of their preferences to do menial work is wrong, it would seem to be better to create them, than to force those who don't enjoy such work to do it.
This is a bit of a false dichotomy - you don't have to force anyone to do it. Offer a sufficiently high salary to scrub Hogwarts' toilet (or just to cast Cleaning Charms on them), and voila, you have free-willed, willing, unmodified house workers.
The meaningful question (at least, to the degree that any moral question can be meaningful) is whether there is any value in that "unmodified" qualifier.
They still don't enjoy the work, even if they find doing it instrumentally rational. They are forced to do it by circumstances, and in a better world they wouldn't be.
ETA: There is now a third thread, so send new comments there.
Since the first thread has exceeded 500 comments, it seems time for a new one, with Eliezer's just-posted Chapter 33 & 34 to kick things off.
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