I've got a TransforM4 which was the first of the latest batch of ICS (trumping the CXP range)
Is damn good rifle, flawless, never missed a beat. As for battery, that's just a simple rewiring that's often necessary in airsoft guns, and I found it pretty easy to fit nunchuck lipo's into the front of mine anyways.
I had to make the ICS vs G&G decision myself, and after talking to lots of techies, store owners, players, came to the conclusion that G&G are far far more prone to issues and not made as well. ICS have put more effort into designing their own guns and gearboxes, rather than just cloning the dimensions of TM and then trying to put cheaper internals in it like most.