The search engine seems to work as well as other forums... most of the time.
You can't expect it to have the power of Google.
If I find its not returning results for something I know is there, I simply use google and prefix the search item with 'geoexpat,'
It partly works. There are certainly mails missing in the search results though.
Example, when I search the forum date sorted for 'taobao' this one wasn't on the first page even though date is very recent.