The most important tactile feedback of a button is not the spring of depression but rather the shape of the button itself. It allows you to constantly reset your bearings. When you're typing on a keypad, for example, you feel whether your finger is hitting the button square in the middle, or slightly to the left or right and adjust accordingly. You can look at the screen and type because of that.
Hell, you can probably type whole paragraphs with your eyes shut without erring. Without the feel of physical buttons, you'll inevitably drift one direction or the other. That's why BlackBerry typing is really so much better than the iPhone. When you have both in broad daylight and are staring at the buttons as you type, the difference isn't as noticeable. But on a Berry, you can text one-handed while driving (though I don't recommend it) while on an iPhone you'd slip up pretty fast. Or, more importantly, you can look at the screen exclusively as you type, as you would on a computer.
I'm not sure if this is relevant here though. Perhaps it will cause your fingers to drift upward when not looking? I really don't know.
Hell, you can probably type whole paragraphs with your eyes shut without erring. Without the feel of physical buttons, you'll inevitably drift one direction or the other. That's why BlackBerry typing is really so much better than the iPhone. When you have both in broad daylight and are staring at the buttons as you type, the difference isn't as noticeable. But on a Berry, you can text one-handed while driving (though I don't recommend it) while on an iPhone you'd slip up pretty fast. Or, more importantly, you can look at the screen exclusively as you type, as you would on a computer.
I'm not sure if this is relevant here though. Perhaps it will cause your fingers to drift upward when not looking? I really don't know.