Ask HN: What Search Engine do you use for your site?

On http://www.romku.com I've deployed Apache Solr to provide the search. There are about 100K documents and it works really well (in particular, I like the faceted search). There are several alternatives (Lucene, ElasticSearch, Google Custom Search, Xapian, SpynxSearch...) and would like to know which ones you have tried / are using. Which one would you recommend.

I've started a list here: http://www.romku.com/list/343869/search-engine-tools, feel free to add more in the comments below and I'll add them to the list. There's also http://www.romku.com/compare/148361/174594/324699/343868/150199/343870/253080 for a features comparison matrix.

PS: I'd like to start a series of posts asking which Tools are used by the Hacker News Community (Bug Tracking, Server Monitor, Analytics, Invoicing, CMS, Web Framework, Database, CRM, Screencast Tool). Would it be useful to you?