Master cylinder isn't an issue.
Don't forget to get the 2.7 dust shields.
I've been running 2.7 brakes for nearly 5 years now. The smaller brakes work very well and I've had no issues, ABS, ESC and traction control all work as they should. The more powerful motors (SDV6 and V8) can overpower the traction control if you apply too much throttle. Gordon from GOE suggested that the smaller brakes could be overworked if the traction control was working hard but I haven't seen that although I do have an e-diff.
I'm running Akebono pads on OEM rotors, on the last trip away I towed my 3T caravan from Sydney down to Araluen which has a steep winding road down to it, I didn't experience any brake fade or lack of performance.
When I wear these pads out (which seems like it will be a while), I'm going to swap back to the original brakes as I'm selling my 17" wheels. I just can't be bothered swapping over wheels anymore now there is some decent AT tyres in 20".

