I use a Sphinx plugin for vb 4.x and it wasn’t complicated to install server side, then install the plugin and run re-index. Then after that, everything ran on its own. I haven’t tested Vb 5.x though which comes already with it.
It might not be urgent to use it atm but it is a very nice and essential feature in my opinion for Discourse. Many webmasters love to use Sphinx search because they know how powerfull and light it is when it comes to indexing millions of data and searching.