When you are using a keyboard and a mouse, or you are using a controller, some keys don't work properly. So if you try to fix it by assigning manually the key to an action in the setting it doesn't work. You can select one actions and when you type in the key nothing happens.

Plus there are some keys that don't work properly:
-Shift for flying down.
-Tab, for autocomplete a command.
-Holding space bar doesn't make you jump more than once.
-Enter when typing in chat.

In this what happens is that when you are in chat with a keyboard, it's detected as if you where typing in the virtual one, but enter only works when you pres the back arrow once after typing the text.

Finally there's a problem with the mouse/cursor. It's not the cross in the screen, it appears apart, and any mouse key works as if you were touching that place on the screen, meaning that:
-Crafting it's funky, and not the normal way.
-Controlling the camera it's very annoying.
-Placing and destroying bocks doesn't work like the PC version.
-The scroll wheel doesn't work, both for scrollig and selecting items.