Recently went to the Montreal F1 with my friend who carries a Sony A200. We were both snapping pictures with 2gb memory cards. After he filled up his (about 400 photos), his batteries needed to be recharged (which was unfortunate cuz we were at the grand prix and he didn't have an extra battery).
My Sanyo Eneloop NiMH lasted me the entire 2gb (~400pics) and an extra 100 pictures of the second memory card. So 500+ photos on a single charge. That includes some indoor flash photography (i'd say about 20%). After my rechargable AA's ran out, i just popped some fresh ones in and kept going
My friend just stood there, wishing he could take more pictures.