When I first read about using fonts instead of images for icons, I was a little skeptical. Particularity from an accessibility point of view, how could the letter 'A' be read by a screen reader as say, an RSS icon for example.
Also, I like to create my own unique vector icons, I bet it would be a painful process to make my own icons into a font for use on the web, I should just stick to sprites.
But having just found IcoMoon I can say my mind has well and truly been made up. Icon fonts are pretty awesome, and services like IcoMoon and Fontello make it super easy to customize and make your own icon fonts.
The great advantages to using fonts for icons instead of images are that they are style-able with CSS, and will look great on retina devices as they are vector based and scalable.