Most of the times, I use Google to search in SO rather than using its own search box, as it returns quite better results. I imagine this is a common task for many of the SO users, so why not including this option inside SO? It would avoid users going out and returning back.
How many of you actually use the SO search rather than Google?
At this moment, I use a custom search provider in Chrome:
Right click on the url bar. Set up search providers. Add a new one.
Name: Stackoverflow Keyword: so url: http://www.google.com/search?sourceid=chrome&ie=UTF-8&q=%ssite:stackoverflow.com
To use it, I just type "so" into the URL bar and hit the TAB key. After that, just type the query and hit ENTER.
This way I'm leaving SO to come back and that MAY not be the best option.