To be fair, there is iPad 2, the New iPad and the 4th generation iPad. They're on the plus side of half, but your point still stands.

The vast majority of them though. The iPad 2/3 were the blockbusters in sales and the 4 is the same as the 3 externally. Few people have the Mini so far and it's pretty obvious cases would not be compatible.

It sounds silly but is one of the least ambiguous options.

Compatible with iPad2 and above (but not mini).

Compatible with iPad2, 3 and 4 (except 3 and 4 are not official names).

Compatible with iPad2, the new iPad and the newest iPad???