The battery grip not that necessary to get it now. It allows use to shoot comfortably in portrait-wise and extra battery power. However, D80's battery life is IMHO one of the best in the market... I've heard ppl claim that D80 battery life = D200 + batt grip.
Unless you die die shoot portrait most of the time or want to look "pro", there is little use of a battery grip. And if you just need the extra backup juice, just get a 3rd party battery eg,Eastgear (got mine there). It lasts longer than the original Nikon batt.