There are two ways to reserve your iPad for the April 3, 2010 launch date, you can pre-order it and have it delivered to your US address, or you can reserve one for in-store pick up at one of Apple’s US retail store. In either case, Apple limits the iPad pre-order to 2 units per customer. I guess this limitation is to warn off grey market sellers, ensure enough early adopters get their iPad’s, and less likely is the rumor that supplies of iPad will be low on launch day April 3rd (in USA).
There are two specific lines of iPad’s, one with WiFi only connection and another with both WiFi and 3G connections. Which one you buy really depends on how you plan to use the iPad. The great thing about the iPad is that its use will depend on the user and the apps s/he choose to install onto the iPad. People have to stop slotting the iPad into any existing electronic device categories. It is definitely not a “tablet computer” in the traditional definition or a “notebook” or “netbook” computer, so comparing it to any of these are like comparing apples (sorry for the pun) and oranges.