Good reply!
What this then comes down to is which we value more highly, utility or truth.
Well I suspect we value believing in other minds and the past and future cos we believe in them, not because there's utility in it. I think we view our inability to disprove solipsism as more of a logical puzzle, like the ones by Zeno of Elea, rather than something to take seriously.
But this just places intuition above logical proof, I guess.
RE: Decartes' Substance Dualism