iTunes has really made iPhones extremely frustrating and antiquated compared to other smart phones. Apple, by trying to "protect" their iTunes content from being "shared" or "stolen" through forcing iPod/iPhone/iPad users to ONLY sync with one computer at a time has probably lost more revenue than if they made the process more user friendly and open like other devices.
You have an iTunes ID, THAT should be the ONLY factor iTunes considers when allowing content to sync from a computer to a device. When you purchase an app/video/audio product on iTunes, the liscense should be synced to your iTunes ID in the cloud.
Then, you can sync to multiple iTunes instances on multiple computers simply by having you sign in to your iTunes ID.
Further, Syncing is dumb. Apps like Dropbox, Google Music, Google Drive, USB Flash etc. allow you to just drop a file or folder of music/video/documents onto your cloud-synced folder and you can play them directly on your iPhone.
I wish I could just delete my "iPod" app all together, I'll play all my music and podcasts through google drive instead.
Then, I'll buy an android phone when my upgrade is available.