Android users have always cherished the openness and customization given to user interface of the operating system with the help of 3rd party apps. While some companies restrict the user interface of their mobile operating system from being tweaked by apps, Google has always made it easily available for the android users.
As a result of open source, the companies add their own custom user interface over the stock android. Let it be the app launcher, widgets, keyboard, apps, etc they look different in different companies smartphones even though they are running the same android Os platform.
When it comes to third party apps you download from the Google play, there are wide variety of apps which can truly give a different feel to your eyes by customizing the user interface of your phone. When we use smartphones, we definitely type using the on screen keyboard and different companies have different user interface for the keyboards. As a matter of fact some of the companies provide keyboards which are difficult to type on, some makes errors, some are not spaced according to your thumbs and many provide features like slide to ease the way you type.