I have a site that I want to resize the text only if the title is not filling a line.
This short title could be larger - want it automatically filling the width: http://allaboutchris.org/blog/2012/being-judas/
Whereas this long title, I want to keep at 44px, since it doesn't need to be any larger: http://allaboutchris.org/blog/2012/why-windows-8-is-going-to-be-rubbish-lowrys-law/
Typically you set the compressor to shape your text. FitText is pretty hands on in this manner. You might want to look at something like BigText or SlabText for more automatic resizing.