For the next release cycle (presumably 1.5?) I think we should really try to stick to released versions of Lucene, and not use dev/trunk versions. Early in Solr's lifetime, Lucene trunk was more stable (APIs changed little, even on non-released versions), and Lucene releases were few and far between. Today, the pace of change in Lucene has quickened, and Lucene APIs are much more in flux until a release is made. It's also now harder to support a Lucene dev release given the growth in complexity (particularly for indexing code). Releases are made more often too, making using released versions more practical. Many of our users dislike our use of dev versions of Lucene too.
And yes, 1.4 isn't out the door yet - but people often tend to hit the ground running on the next release. -Yonik http://www.lucidimagination.com
