The search section is out of date now, they use the Realtime Lucene branch (with modifications). The link to the slides seems to 404 now, but you can see a video of their presentation at Lucene Revolution here: http://vimeo.com/16063395
I thought that the 55 minutes to watch the video with linked slides was very worthwhile. For me: I need to use pig more often rather than write custom map/reduce jobs; custom pig UDFs deserve a look; liked the explanation of how they tried to use Cassandra to store tweets, decided not to, but how the will be using Cassandra for other tasks; etc. Really interesting stuff.
