I have only tried it for an hour or two, and can't speak for its search result quality, but it seems promising.
On my laptop, with an index of 10,000 documents each containing 200 random words, it takes about 110ms to perform a fuzzy search. Half of that is the actual search, the other half is the process/initialization overhead.
It's written in C++, and the core features are performance, simplicity(operation and extension of functionality) and a sane, simple API (the codebase is quite small as well, at about 14k lines of code).
Its similar in some regards to Lucene, but does away with most of the exotic features and instead is optimised for rich queries support, fast execution and extensibility.
It should be on GH sometime in April.
Maybe I should reconsider?
The reviewed tools were: clucene, Apache Lucy, Indri/Lemur, Xapian, and Zettair. Of those, only Xapian and Zettair could be made to return useful search results within time constraints. Sadly, I didn't get Apache Lucy to build, which along with Xapian is the only option still being maintained. clucene could be built, but delivered erratic results (it found "impeachment" but not "indictment" in the US constitution text), and was too difficult to extend into a full stand-alone app (though it apparently is being used in Informix still).