I must admit I don't know what Apple is using for battery in iPad but I'm really impressed with how long it lasts.
Be sure and set your Auto-lock to Never so the screen stays on and that will deplete the battery even faster. When my battery level drops to about 20%, I put on "Hunt for Red October" and let it play in the background. A few more times and I will have the entire dialogue memorize... both the English and Russian parts! If I ever go to Russia I am all set since I now know the Russian national anthem by heart!
If you have seen the teardown, the ipad is literally an iphone 4, with the rest filled up with battery packs. That is, take an iphone and place it on top of the ipad, that much room is actually motherboard and sensors, etc. The rest is battery.
I got some app for a buck, called battery pro HD, it's cool, it talks tells you the battery level, also tells you avg time you have left for games, surfing web, etc.. It's decent.