Microsoft says fix for "other" storage issue will come, offers a solution
Judging from the tone of the tweets that have been sent to Joe, along with the number of threads that this problem consumes on the Windows Phone website, this is a hot-button issue that is affecting a lot of users. One app that seems to help, if you believe user's comments, is called Shrink Storage which is available from the Windows Phone Store. A few users said they were able to re-claim 1GB of space and more. It's a free download and is designed to fix the "other" storage issue.
source: @joebelfiore, WindowsPhoneDaily, WindowsPhoneStore via WMPoweruser