iOS and the “Other” Capacity

Recently I updated my iPhone to iOS5, which was pretty painful because after I successfully loaded the new version on my phone I figured out that something was reducing disk capacity. In iTunes it is marked in the capacity bar as “Other”. And this misterious “Other” reserved more than a gigabyte and a half on my Phone. Unfortunately I bought a 16GB iPhone so I lost a lot of space and I needed to get rid of it. Anyways I never figured out what this “Other” was and I couldn’t find a good solution for this. After trying to clean with a backup (this son of a b**** was also in my backups) I had to restore it to factory default and sync everything from my computer again… Maybe someone is smarter than me and can explain what this “Other” was.