4 gigs??? dang that's high.. most people say that other is the OS, but I've always thought it was just the apps. and maybe contacts and things. I always thought the OS was the extra amount of memory that you aren't alloted to use. like i'm supposed to have 16gb but i only have like 14.5gb available. I thought all that overhead stuff was the OS.
Basically I don't know, but 4 gigs seems insanely high. I have many many apps and I'm pretty sure my other is around 3gb or under...