Well, the word handed down from on high is that as soon as you plug your iPod into another machine, you are presented with the choice of wiping the iPod clean and making the new machine the sync machine. Otherwise the iPod will not work with that machine's copy of iTunes at all (or so is the impression given).
In theory, of course, you could just copy the files via firewire hard drive mode.
My guess (my iPod hasn't shipped yet, grumble) is that iPod lists its contents similar to Rio's and other MP3 players. You're probably able to manipulate its contents, but not play those contents. But that's just my guess, since my iPod hasn't shipped yet (grumble^2).