i'm a bit confused...Are you meaning you're getting a battery Grip?
if so, those hold 2 batteries, and so you will need a second battery anyway (it works with 1 if you need). The battery grips don't come with batteries unless you order a package deal.
"Bulk" is a plus, believe it or not... actually not a downside in most cases.
Downsides... expensive. Cheap ones sometimes don't work well.
I'd go and check if the grip is comfortable first. On a smaller camera it may be a hinderence more than anything. I know the D80 grip feels bad to me, the D200 great. That said I know someone else who thinks the opposite.