Haven't used, but some first hand ideas
- the overall performance with long lists of threads? Will it kill the application, whole phone?
Would be nice if you can cut / end certain conversations and e.g. store them to Ovi mail from the phone, before they get too big, before they vanish otherwise...
ovi suite already stores messages in conversation style, so you can delete some messages on phone to shorten the conversation after you sync them to pc.
Another suggestion in addition to the Ovi backup/sync..
1) An in-phone solution is to archive the old messages - say once a max of 50 messages in the thread is reached, archive the oldest 20 messages in the thread to give room for 20 more. The archive is then stored into the memory card in some readable/reloadable format. Just have a link at the top of the thread "View older messages", and vice versa to go back, "View newer messages". Of course these have to be properly implemented in such a way that even when the contact is deleted, the sms threads/archived threads remain backward readable.
or
2) Have an auto-purge option for messages older than x number of days, or keep only last x number of messages to keep the memory in check. The user should be given the option to have this turned on or off. This is for people who are not fond of syncing their devices.