I had the same "other" space problem on my iPhone 4. I followed the advice to unsync all data except apps, and that seems to be working. But honestly, this is an iCloud issue. As soon as I turned off all the iCloud syncs, the other space practically disappeared.
I might be the only man in the world to say this, but I like MobileMe and I use the iDisk cloud a lot with zero complaints. I'm writing a book, so I type on my computer and then backup to multiple sources, including MobileMe. Then, I can at random take a look on my iPhone at the document, or at work maybe visit mobileme.com and take a look, share the file from there, etc. With iCloud, my understanding is that I have to use one of the Apple apps (cough* $$) to then share this way.