I think adding a site setting that allows you to pick default site sort order would be useful in some cases:
I agree with @codinghorror 100% that our default of “Relevance” is correct, but can see cases where there is a very strong preference for latest (either post or topic).
I am not keen on making this a strong per user setting quite yet though. @codinghorror should we slot adding this site setting, or wait on this for a bit?