You have two main models one that connects to the web using Wi-Fi and one that uses a combination of Wi-Fi and 3G wireless from AT&T.
Wi-Fi models come in three capacities starting $499 for 16 GB, $599 for 32 GB and $699 for 64GB. The 3G equipped models come in the same capacity but sell for a 130$ more. Apple promises a 10 hour battery life including web and video and about a month of standby time. The highlight of the iPad in the long run is definitely going to be the Apps made by third-parties. There is already the video streaming App from NetFlix and the comic App from Marvel.