Is there documentation on the available prefixes? Because they are damn useful.
There used to be documentation on the old extension page [1], but I guess that wasn't very clear. It used to be possible to define your own subsets of namespaces as separate prefixes, but that somehow didn't get ported when we switched to MWSearch. Here is an overview of current functionality: Prefixes: * all - searches all namespaces, e.g. all:kurt vonnegut * <namespace name> - search one particular namespace, e.g. wikipedia:deletion * <ns1>,<ns2>,<ns3>,... - search a list of namespaces, e.g. help,help_talk:tables * incategory - search articles in category (when category is added directly by the article and *not* via template), e.g. incategory:"Living people" incategory:"University of California, Berkeley faculty"
the last one gives a limited mock-up category intersection capability (don't trust the highlight there :), which could be useful for testing if someone would want to make the category intersection frontend.
r.