Hi Batman,
I think this is someway related to what I was doing with my wife's iTunes library recently. We do have two iPads 2 plus an iPod Classic and I wanted to use one iTunes library only. I am not an expert, but this is what I've found during the 5+ hrs I invested fixing my issue.
I think that "offically" you can only sync with one iTunes library. You can use several devices with one iTunes library though. If the device detects that you have synced with a different one, will ask you to wipe out content and upload. You will say NO! What I did or what you need to do, is for the one you want to use at home or being the primary, you select upload purchases instead. Once done, you will transfer whatever you have on your iPod or iPad and keep it on the laptop.
Now, in terms of sync, I think you can also opt for what to sync and what not. If everything is checked, like songs, every time you plug your iPod or iPad will try to sync or upload all the stuff you have locally ... the result? You end wiping out your iPod or iPad content.
The way I transfer my songs and mix that with my wife's was this:
-I imported the songs via iTunes using a SAMBA share (you can share a folder on Windows too) This is because my songs were on a Linux server
-Once imported on my primary, my Mac air on this case, I will see the content or songs, but of course, they are not locally yet.
-Click or select all the songs or content and select "consolidate"
After a few minutes or hours (depending of how many songs you have) the content from one iTunes share will be copied to the second one. And the destination or primary will have all your content there.
To keep in mind:
You need enough permissions on source to be able to copy, browse and share via iTunes from the second computer. That was a problem for one of my songs/folders.
If you library is big, consolidate by chunks. Sort by added date and work in batches
Say hi to Robin from me ...
