There are only advantages in using Font icons than using Image based sprites.
- Font icons scale very well. Be it a retina display or any low resolution display, they look good everywhere.
- Font icons can be customised using CSS. You can change the height, width, color, margin, padding, etc very easily using CSS. If you go with Image based sprites, these changes would be a nightmare.
- Font icons fit well with other text on the screen. They adopt the default line height automatically.
- Only one HTTP request is made to load a font icons file. Hence, the only advantage of using Image based sprites is also available here.
Go and use Font icons without worrying about anything. It's time we make better web applications. :)