This is really easy to do and works very well on Kubuntu 12.04

1. NB Do not plug phone into usb to start with. (I made this mistake many times)

2. On phone open 'Menu - Settings - Wireless and Network - usb utilities'

3. A message will appear saying 'Tap button below to copy files between the computer and SD card', tap the button.

4. USB Utilities pop up box will appear telling you to connect usb cable, obviously do it now.

5. The little green robot will appear telling you, you have connected your usb cable, However you still have to press "Connect USB storage" at the bottom of the screen.

6. At this stage a popup box will display in your system tray asking you which action you want to use for this device, choose File Manager and Dolphin will open up showing Android UMS composite and all it's folders.

From then on it's just a matter of splitting dolphin and dragging and dropping as you like, easy peazy. I found that the best place to copy music to was the Samsung/Music folder as then it is easy to find on your phone.

7. When finished NB, before you remove the usb cable, remove the device from the usb device list in the system tray and also press 'Disconnect storage from PC' on your phone.

One last thing copying and moving folders and files via dolphin in this manner is very very fast