One of these days I hope they'll add the ability for me to sync my iPhone to iTunes at home and listen to it on another PC (most specifically the office) from my iPhone via iTunes without some horrible hack and manually managing my music collection.
I was under the impression that this already worked.
You can't copy the files off (without some 3rd party software) but I thought you could browse and play via iTunes. I remember it being clunky enough that you might not want to do it regularly but I thought it worked for playing a couple of tunes.
I haven't been able to figure it out if you can. In order to see the music and actually play it (where it's not grayed out and unclickable) I have to set my music to be manually managed on my PC at home, then I need to get the iTunes library key from the file at home and inject it into the right spot in the same file on any other PC I want to listen to the music on.
I actually just stopped putting music on my iPhone because it was too much of a hassle to do every time that key changed. I just use Pandora or GrooveShark now instead.