Darel Rex Finley recently published an excellent article explaining sub-pixel font rendering. It’s an interesting subject – when LCD displays first became popular, every major OS vendor rushed to add this feature. And it basically looks good for what it’s intended for – black and white text.
But this breaks down as displays get more sophisticated. Even though this feature is turned on by default on my Mac, many advanced graphics features bypass it. For example, in a web browser, if you add a text shadow with CSS, you don’t see sub-pixel font rendering. And it doesn’t work if your display is rotated, something that happens often with the iPhone.
In fact, the iPhone is interesting in that it doesn’t use this feature, largely because its display resolution is so good that it’s not really necessary, and also because you can rotate the display. That’s another place it breaks down – the feature takes advantage of the arrangement of the red, green, and blue colors that make up the display, and once you rotate your display, it would have to work in a completely different way.
So it was good while it lasted, but I think its days are definitely numbered, as displays get better and better. I’ve had mine turned off completely for a while now, because I no longer like the way it looks, and I think more people will agree in time!