Dummy font renderer et al?

[tummychow]

I just read on Lifehacker about how to fix the font cache problem. I understand roughly what is going on when the font cache is being rebuilt. But I never actually experience hangs when the font cache rebuilds; it's just that sometimes I'm a little bit impatient to get to whatever it is I was going to watch. This means that changing to the dummy renderer provides me with no stability/bug-fixing benefit.
So my question is: what exactly is the difference between those text rendering modules, besides the fact that sometimes, one of them locks up? Am I totally misunderstanding the matter at hand? Any pros/cons that the end user should be made aware of if they are considering switching to one or the other? (Aside from the occasional freeze up when the font cache is rebuilding.)