The current Arduino toolchin (AVRGCC etc) does not support the new chip hence it was required to update it. However instead of updating the existing toolchain, we decided to use the new tool chain just for the board. The platform allows inclusion of tool-chain for a specific board. Picture below shows the setup that works on windows.

Similarly we did tests on Ubuntu 64 bit. We believe it would work on other linuxy/unixy machines.

The detailed steps can be found on the tutorial below.

http://exploreembedded.com/wiki/Tit,_a_supercharged_Arduino_Pro_Mini_with_Atmega328pb

We would need your help in testing this on other unix/linux machines and see if works. Also testing it on other versions of Arduino Software will be of great help. Please do comment if you've any concerns.