A slightly deeper conclusion is that we tend to care about other people's utility more than their happiness (for example I would not consider 'they won't be unhappy about it for long' an acceptable justification for blowing people's legs off).
This is sloppy thinking -- I find the example much more easily explained by the fact that happiness is a vague metric, that we can't easily affect directly, while number of legs is a concrete metric and an amputation measurably decreases said number.
But if you ask me whether I'd prefer to be happy and legless, or constantly sad and legged, and I'd answer the former. So since I'd prefer the former, how can you say that the latter has more utility?
A distinction that some people grok right away and some others may not realize exists:
This is also somewhat a reply to Hanson's "Lift Up Your Eyes" on Overcoming Bias. Some people on LessWrong are careful to make the distinction between ordinal utility, cardinal utility, and fuzzies, and others aren't quite so much. The above sentence on accepting evidence and the post script that he is not serious about one part of the post might also make interesting conversation -- part two is advice to move next door to a child molester for cheaper housing if you don't have a kid and part three is about The Fed taking advantage of banks.