After being extremely frustrated going from home to work getting denied by the music lock-down that is iTunes,
I had to find a way to get my music.
The problem in general: you load up iTunes on different computer than your first / main installation, with lots of music already on your iPhone/iPod, and additional music on the additonal computers being used. iTunes will let you scan your computer for music automatically, and add what it finds to your library, but here's the kicker- as soon as you try to Sync and get the music added on it warns you that doing so will OVERWRITE all of the existing music on your device! What good is that??? I just wanted to add another album, not LOSE EVERYTHING I already have!
My specific problem was this: I'm going from home (one iTunes installation where my entire music collection is) to work (another iTunes installation with a couple albums I ripped), and I'm getting more music in both places occasionally, (from ripping CDs that I own of course ;)... I asked someone at work how they were getting music from their home computer onto their iPhone, and then music from work onto the same device, without overwriting anything? They told me to do what most people do- burn it to CD at work, and then rip it using iTunes at home and it will get added to your library... Well, that's not good enough, because I want it in my playlist now- for the love of God, isn't this the future?
Finally, after some searching, I found a way to get it to work using WinAmp.
There is a plugin called ml_ipod that will download everything off of your iPhone/iPod onto your hard drive. (click here to get ml_ipod from sourceforge)
You can then combine your other music with it in one giant consolidated collection, and then let iTunes wipe over and import all of your music into the iTunes library from your hard drive (now that you have everything that was on your device), and do a full sync - ok'ing the fact that iTunes will overwrite the existing music. As far as I know / can tell, there is no quality loss.
I hope that helps some people who are dealing with this annoying system. And Apple, if you're reading this- stop getting so Mircosoft on everybody, it's not cool anymore. Don't make us start mocking your commercials where you try to look so different.
Additional Resource (for getting iPod / iPhone music on to your computer and then onto other devices):
http://www.iskysoft.com/article/video-from-ipod-to-computer.html