I have GDR3.I can say that GDR3 has greatly improved my battery life compared to 2.And about the overheating thing,while playing games like odern combat and spiderman on gdr2,the phone would heat as hell such that I wouldn't be able to keep touching it.It would be very hot.And now in gdr3,its hot,but with bearable heat.i guess about half the heat as gdr2..but it still got issues,like if you open big apps,,close,open another,close,i.e. things that take up memory,it begins to heat even when idle.th last resort is to reboot the phone.Also,i had recently download a game,i forgot.it was multiplayer,good graphics,185mb file size.my 920 would just freeze and only soft reset could help.happened twice.now the game is uninstalled.so far,battery life is way better than gdr2,especially while browsing