September 19 Update
As of the deadline to report our preferences, this question has two answers in favor of unpinning and no answers opposed. Given that the overwhelming opinion is in favor of unpinning I have made our preference known by editing it into the answer on the main meta site.
It sounds like the change will happen in mid-October.
As discussed on the main meta site:
[On Stack Overflow we] no longer pin the accepted answer (with the green checkmark) to the top of the list of answers. By default, we now sort strictly by votes (descending order by highest score), and the accepted answer's order in the list is based on its score.
We can change the way the engine sorts answers in site settings. We would like to hear from you all if it is something you want to see on your site. (Please let me acknowledge in advance that we will not be able to run a test on each site.)
This would affect about 850 questions on our site. I'd recommend looking at some of the highest and lowest scored accepted answers from that query as well as some of the highest and lowest score differences. You can sort the query output by clicking on the column headings.
Would we like accepted answers un-pinned from the top on Webmasters? We have until September 19th to give our feedback.