I've created a plugin that extends the existing Sprite font native plugin to include richer support for individual character widths during both editing and runtime. It works really well when used in conjunction with Blackhornet's Give Your Font Mono(spacing) Sprite Font Generator.
You can download it over on codeplex and I've updated the documentation there to show how to use it as well.
The primary benefit is being able to use custom character widths without any extra events and full support while editing. Here?s how the 2 plugins look in the edit window versus runtime when the extra events as described in the documentation are used for the native sprite font object:
<img src="http://thechriskent.files.wordpress.com/2013/11/image_thumb23_2-1.png" border="0">
They end up looking the same but the native plugin is a lot harder to work with when using custom character widths.
Here's a tutorial I wrote to help you get started.