Well, in Nutch we simply replace the two jars and it all still works.
> The CHANGES.txt file in branch_3x says that the javabin format has > changed in Solr 3.1, so you need to update SolrJ as well as Solr. Is > the SolrJ included in 3.1 compatible with both 3.1 and 1.4.1? If not, > that's going to make a graceful upgrade of my replicated distributed > installation a little harder. > > Thanks, > Shawn