iPad have a single physical home button which those don't have and that's something that several manufactures coped. They could use 2 buttons on the same side or mirror the bottom button on the top or offset it from the center or add some lights or even simply change the edge color or add decorative divots in the outside corners etc. http://en.memory-alpha.org/wiki/File:PADD_2150s.jpg
But instead of picking one of the trillions of other designs they used the iPad design because it sold well.e