Even with CSS Sprites, there are two requests - one for the CSS, another for the sprite image file.
The main advantage of CSS is that you can change the color and appearance of components without using a graphics package, and they might scale better. But that's about it.
It was a technical exercise rather than a proof of concept. The icons themselves are very simple and limited. I wouldn't recommend using CSS in this way for production work (other than perhaps for very simple arrows).
This has the added benefit of screen reader support.
edit: I'm not sure why I can't reply to you below, but here are some of the unicode arrows:
It's easy enough to get screen readers to ignore it, if it is truly presentational.
But there doesn't seem to be one for the simplest: just a basic triangle.
It's a nice theoretical challenge, and may provide some benefits if you are building (mobile) device specific systems, but as a broad technique there is little production value at the moment.
OTOH, I don't know that there is any way to take these icons and draw them at a larger size without creating new CSS.