I have a 16GB iPad (iOS 4.2.1) without jailbreak and used to manage musics and photos with iTunes in Windows. I just have tried to sync iPad in my Ubuntu 10.10 64-bit installed aside Windows 7.
When I first plugged in iPad via USB, an error window pop up with “DBus error org.freedesktop.DBus.Error.NoReply: Message did not receive a reply…”, then I fixed it and got iPad to sync with gtkpod(Rhythmbox works too) by upgrading “libimobiledevice” to the latest.

1.) Check libimobiledevice version in System -> Administration -> Synaptic Package Manager, it’s recommended to uninstall libimobiledevice0 if installed.

2.) Add ppa:pmcenery/ppa and install the latest libimobiledevice1 package. Use the commands:

sudo add-apt-repository ppa:pmcenery/ppa
sudo apt-get update
sudo apt-get install libimobiledevice1

Now, plug-in your iTouch or iPad device and it should appear in gtkpod(Rhythmbox):

Thanks to xlash from ubuntuforms.org posted the solution.

PPA for Paul McEnery: https://launchpad.net/~pmcenery/+archive/ppa