Editors' take: The iPad's bigger screen real estate lends itself well to tower defense games such as Plants vs. Zombies HD, a $10 game where players attack hordes of zombies.
The iPad-optimized version brings the game nearly up to parity with the versions found on PC and Mac computers, which cost twice as much. This includes the proper top placement (instead of the side) of all the weapons and resources you must work with to defeat your zombie foes, as well as survival mode, which lets players try to stay alive for as long as possible. For many of those who have finished the game's campaign, this is the mode of choice, and something that was sorely missing from the iPhone version.
iPad users also get a new (and exclusive) minigame mode called "buttered popcorn," which makes use of the iPad's multitouch display. In this mode, players can select up to 11 zombies at one time, "butter them up," and then unleash popped corn kernels via corn cob cannons. Presumably, by selecting "11 at a time," PopCap means players are expected to use their nose, or the help of a friend, to select the extra zombie beyond their own 10 digits.