On mobile devices, there is absolutely no room for error. No room for blurry pixels, no room for confusing icons, no room for user experience mistakes, no room for sluggishness. The entire device is one big constraint: a flat piece of glass that accepts touch input with a few millimeters of metal chrome around it. That's it. All you have is the glass and how things behave under the glass.

If things under the glass move as you move your finger, the illusion of direct manipulation of a digital interface is created. If you move your finger and, then, a split-second later something moves in response to your movement, that breaks the illusion. Apple has fully understood this from the beginning, and the iPhone has always responded to pinches and flicks with nearly 1:1 accuracy, especially in the browser, which is where iPhone users (myself included) seem to spend most of their time.

Android, on the other hand, has always felt laggy to me. I've used the Nexus One, all the carrier versions of the Galaxy S, the Nexus S, HTCs, Droids, the list goes on, and none of them have felt right-on-the-button perfect when I move my finger around on the screen. I move, the phone processes some things, and then the interface moves. This has been the Android way since Android's inception. The built-in browser is the most egregious example of sluggishness, especially when pinch-zooming or double-tapping. Check out this video of an iPhone 3GS vs. a Nexus S. Astoundingly, jaw-droppingly bad.

Now with this in mind I just saw that the Galaxy Nexus, the new supreme king of Android phones, has been unveiled. This Is My Next has a hands-on review and this is the single line that stood out to me:

The subtle, pervasive lag that has characterized the Android UI since its inception is still there, which is not a heartening thing to hear when you’re talking about a super-powered dual-core device like the Galaxy Nexus.

Pervasive lag? On a mobile device that's running the very latest Android version? Powered by one of the beefiest mobile processors in the world? Samsung's cream-of-the-crop phone running Ice Cream Sandwich is still, still laggy?

Totally fucking unacceptable.

Imagine if your mouse cursor couldn't keep up with your hand movements, or if letters didn't appear on the screen until a moment after you pressed your keyboard. That's how egregious of a user experience problem this is. If a user interface doesn't respond as quickly as possible to a user's intentions and movements, it's a pile of rubbish. Immediate touch response has been solved by Apple for years, why can't Google and Samsung and Motorola and HTC solve it as well?