There are a lot of threads regarding voiding warranty if you launch the GTR with R mode off and you have a transmission problem due to the launch (I believe some have had theirs denied even when the transmission failed sometime after the launch).
The R mode off is to disable traction control so it doesn't interfere with driving on a road course for those drivers who can push the GTR to its limit without going off the track. I would suggest leaving traction control on while at the track until you push the GTR hard enough to intervene. It was not initially designed for launching as per Nissan.
With R mode off you will also get a better launch due to the traction control not acknowledging wheel slip and cutting power (maybe someone can correct me, but in the 2010, don't you have to have R mode engaged to launch?