I have not used this version but I did try and use an earlier one and it was slow, went through AAs much too quickly and left me very disappointed. This newer model may be better but I would want to try it out before purchasing.
Well, there are limits to how energy efficient these things can be. A harddisk uses power.
I'm not entirely satisfied with the battery performance of the Epson P2000 myself, but it's enough to copy a few CF cards, and it lasted me long enough to give me a chance to recharge it while I was going from hotel to hotel in the far east.
But the P2000 wouldn't cut it for an intense shoot in the wilderness without some backup power, such as the Digital Camera Battery (http://digitalcamerabattery.com
, if I'm not mistaken).
So, how quickly is "much too quickly", and did you try to use rechargeable batteries (e.g. GP's 2500 series or better)?