What I recommend for precision/recall /config options is that your platform (rails, django, java, PHP) probably has plugin for SOLR and sphinx. Set up 2-4 indexes using the config options that matter most to you (for me they're AND-OR of search terms, and stopwords, which i use in lists of 0, 50, 100, 150). Then do a (sort of) A-B test where you see which records one index picks up that the other misses. (Most people recommend not using any stopwords if you're only using one index, but i never got decent results using only one index)
P.S. Solr is the 800-pound gorilla, has the terrific Manning book, zillions of docs, etc. Sphinx probably covers most people's needs config-option wise(at least for European languages) lightning fast to index, and runs in 256M VPS, no tomcat/jetty.