Base-10 absolutism rears its head again. The objection to 1/3 is that it has a non-terminating decimal expansion. This is not a problem if you're using base-anything-with-3-as-a-factor.
What about 1/5 instead? There's always going to be problems with some base, the point is that unit conversions are super easy with metric, and it's easier to teach to children.
As for temperature, 0 is really gold and 100 is really hot in pretty much every scale, that's just a very subjective way of describing things.
Base-10 absolutism rears its head again. The objection to 1/3 is that it has a non-terminating decimal expansion. This is not a problem if you're using base-anything-with-3-as-a-factor.