Sometimes you want to combine Font Awesome with other fonts, e.g. when you need alphanumeric characters.
In Example 1 below, the "quick-and-dirty" approach causes the A (and its label) to be placed too high, compared to the B. Also, this will look slightly different in various browsers - and probably none of them will look OK.
In example 2, I solved this by using an "invisible" Font Awesome character, so that everything (i.e. the label) is placed in the correct spot. Then the A is placed on top of that.
Not the most elegant solution maybe, but this was the only trick I could think of that gets the label in the correct place in all browsers. The position of the A relative to the label is a bit browser-dependent, but close enough so as not to bother me too much :-)