One of reasons to setup my own Jabber server was to be able to store history on server while having data under my control. I use Jabber clients from several locations and having history on the server seems to be logical step.
Unfortunately implementations of XEP-0136 are a bit lacking. During install I enabled mod_archive, but it was not using up to date specification and there is no client which works with it, so there was no way to view data in it. Recently I found out that rewrite of this module exists - mod_archive_odbc. It is implementing current version of XEP-0136 and is using SQL database for storage (so at least writing SQL query to grab data is not that complicated as with Mnesia database used by original version).
Migrating of current history went quite good using wswutils, at least I did not notice any problems so far. The only problem is no support from clients. The only reliable way which works for now is Jabber archive web reader, but I'd really like to see integration in Gajim, any volunteers? :-)