It's customizable in the LESS or SCSS.

That's quite good.

My guess is to avoid polluting the class namespace.

Correct. And it is customizable as a variable.

I can't tell you how happy I am they changed this. No more icon-* conflicts. I've had issues with duplicates with bootstrap's built-in when I only want certain icons to be glyphs, or if I want to create my own. I actually had to do an override where only objects with icon-* and a css class of font-icon would render from the font.

It'll take a little bit of work to update, but I definitely think it's better for compatibility-sake.

Oy I didn't see that. Oh man.