Yeah, I do the factory reset once every few months when the "other" starts to accumulate. In my experience, a lot of this occurs when you have failed app and music downloads. I use iTunes Match, so I delete and reload playlists all the time.
With iTunes Match, I can no longer sync locally, so everything has to be downloaded from iCloud. If the download hangs at any point, then it takes up the full amount of space, if if the download failed to complete or the file is otherwise inaccessible. There's no way to get rid of this dead space unless you do a factory reset, and then restore from backup.
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The only successful options I've had is to completely resort it as a new device; no iCloud backup. You will loose your settings and some app data (some games store your files in iCloud so when you sign back in they will be there).
It's a pain, but it's a "clean slate" if you will and will get rid of "other", which could be the result of corrupt syncs.
The factory reset as a new device is how you get rid of "Other" space that iOS takes up from corrupted syncs, etc. But, the restore can (and IMO should) be done locally. Just make sure that you do a local back to iTunes and then restore from that backup.
Some of the "Other" space can also come from misbehaving apps that take up a bunch of cache space and don't provide any options for clearing it out. If the "Other" space is taken up by apps, then you can clear it out by only performing the Restore from Backup. In this case, you don't need to do the complete factory reset. Takes up a lot less time and can still flush out a lot of cruft.