Just as a data point, we're using Lucene.Net 2.1 in a production environment with reasonably heavy load (~300k views/mo, most of which touch lucene in one or more ways). With 2.3.1 in testing we were getting a variety of errors, most notably a write.lock issue that would cause index updates to fail reliably even though there was only ever one process writing. After applying the patches, we have no errors and all is running smoothly. (We haven't put it in production yet, but as soon as somebody thinks we should, we can).
--Max
