Its good but it can make general surfers confused. Personally I wont like another searchbox in the results. Its better to go to that site and then search. Though I cant see the searchbox here(72.14.235.104).
It is cool but I would like it more if the box does not appear until I move the mouse over craigslist result or its sitelinks then disappears when the mouse is out
http://searchengineland.com/080304-162923.php http://www.centernetworks.com/navigational-site-search-boxes http://www.searchenginejournal.com/google-tests-search-box-within-search-results/6458/ I found those three stories by searching Google for "search box in results"
Interesting thing ! Google never fails to surprise us webmasters. Btw, that search box doesn't appear on other searches like 'digitalpoint' or 'esnips'.
I see it in FF. I guess if someone is searching for craigslist, a craigslist search box is/could be appropriate/beneficial.