a question regarding the new table "newssync_cache" that was added in b3/b4: if I am upgrading from b2, this new table will be empty. Do I need to purge and re-sync all my forums to get this table populated? Will there be a problem if I don't do that? I am trying not to re-sync because this process takes too long for long groups.
short answer: no, you don't need to purge and re-sync.
more detail: the newssync cache is a replacement for the old .dat and .txt files -- which you can delete if they still exist. when you sync for the first time (with this newer version) it will "fill the cache up up" with this same nntp summary data [which expires as the nntp expires messages]. "new" messages are now based upon a SELECT with a join between cache and the data tables - significantly more efficient that the previous "loop thru all messages every time".
as always it is recommended if you are attempting this on a production system, backup first... of course, beta software is NOT recommended for production, however, I am running it on wineknow.com.