Finally, there is a solution available for the iOS devices big ristrication i.e. syncing multiple iTunes Libraries. This limitation also force users to complies all of their songs by placing them on one PC in iTunes. Although there are many other solution availbale for this limitation including adding music to your device manually from iTunes but its not quite popular and permanent solution. Now MultiTunes Cydia tweak has been released for jailbroken devices which allows users to sync iPhone, iPod touch and iPad with multiple iTunes libraries.
Release notes from Cydia:
From the creator of MyTube, MultiTunes is an app that allows you to sync with as many iTunes libraries as you want!
MultiTunes Cydia tweak works in a way that it creates profiles for each of your various iTunes libraries on different computers. You can add more libraries using the + symbol on the top right of the screen. Whenever you connect your iDevice to a new PC with a new iTunes library, you can give the library a name and sync it with your device. This library will be synced without touching previously synced libraries.
If you want give it a try then MultiTunes Cydia tweak available in Cydia and can be downloaded from bigBoos repo for free.