I dumped ownCloud after it deleted a critical file for some unknown reason. The bug is still open. Maybe the calendar and addressbook handling is better, but I won't be trusting it.
But I do not use it for files. So good to know, that there might be a problem.
Did it "loose" the files, deleting the files from the server, or just the "link" to the files?
There is some kind of strange race condition with the syncing. It doesn't always happen. In fact it doesn't happen very often. But most people won't accept even a "rare" random file deletion from a product they're using to protect themselves from exactly that kind of data loss.
Thank you for the work you've done on ownCloud. It's a fantastic project and it would be my first choice for hosting as I self-host everything. But a client that is willing to delete files instead of syncing them is just not worth risking for me.
Links: http://forum.owncloud.org/viewtopic.php?f=14&t=3148 https://github.com/owncloud/mirall/issues/328