Good post. I solved my mongo full text search problems 2 weeks ago using Ruby's Sunspot gem http://outoftime.github.com/sunspot/.

I walked through this tutorial http://masonoise.wordpress.com/2010/02/06/using-sunspot-for-... on using Sunspot with Redis and had it working with Mongo in under an hour.

For production ready, scalable FTS, you might be interested in Lucandra: http://github.com/tjake/Lucandra, which powers the http://sparse.ly/ twitter search site.

Higher level overview of Lucandra: http://blog.sematext.com/2010/02/09/lucandra-a-cassandra-bas...