Interesting. After years of paying through the nose for a Google search appliance that actually wasn't very good, my company decided to replace it with Solr, and it was a really fun project. We hired the Solr project's main committer to consult with us and in the process submitted patches for bugs that we ran into.

The whole thing cost less than one year of the GSA license fee, we can search all of our content (the GSA had a hard limit on the number of documents it would index), and the search results are way better.