runs on iOS 5…iOS 4 models are upgradable
Available in 16GB, 32GB and 64GB memory configurations. What model you decide to get would depend on how much media you want to download (songs, videos and apps).
The iPad is available with or without 3G wireless service. Check with one of the two available carriers (AT&T and Verizon) for detail on the various plan options that are available from each carrier. Also, Sprint now carries the iPhone 4s, which may mean the iPad could become available in the near future with a wireless plan from Sprint.