As it is today, sorting by vote is largely useless since it allows only to see the all time highest or lowest votes.
I propose to copy another feature from reddit and have add a "last hour", "last day", "last week" "all time" choice to it.
I think it would also be useful to have a couple of boxes on the side to specify a date range in case those presets aren't accurate enough.
This would only be useful for those questions which have more than a few answers.
In other words, discussion, polling, or very subjective questions.
SO Q&A format doesn't really support discussion style questions, and so encouraging them by providing better support for reading them is not likely.
If you can give a few examples of great SO questions that really would be much better with this functionality, it would go a long way toward convincing the powers that be that this feature is necessary.