Read anandtech's review. He was predicting that the Note 2 would have better battery life on LTE than on T-mobile's 42mpbs gsm network. Apparently the new LTE modem on this device is extremely efficient. This would be very exciting if it holds true.
AnandTech - Samsung Galaxy Note 2 Review (T-Mobile) - The Phablet Returns
"On T-Mobile DC-HSPA+ the Note 2 also does pretty well, it?s in the upper third of our results, still above the SGS3, and among other phones I subjectively consider to have great battery life on cellular like the One X (8960). I suspect if I had been able able to get the Note 2 on AT&T LTE (more on that later) we?d see even better run time thanks again to the race to idle advantage that you get with the faster air interface." - anandtech