Since Android is open source companies have taken the OS source code and modified it to fit thier devices. Also, end users or device manufacturers are able to write a program called a launcher that changes the look and feel of the device. This is one of the beauties of Android over say iOS where everyone is stuck with the same old grid of icons. I believe HTC's UI is called sense and Samsung is called Touch Wiz, something like that. I have an asus and I stuck with thier layout. I also have a galaxy tab and I actually ditched Touch Wiz and downloaded Launcher Pro from the market place, I think it's better than TW. I would download a few launchers and see which one you like, since they are just programs it is easy to switch between them.