So far it seems like it is not fluent, but choppy. E.g. if you have one state attribute with font-size: 14 and want to animate to state with font-size: 16, the
Check out http://www.zachstronaut.com/posts/2009/08/07/jquery-animate-css-rotate-scale.html
You will be able to see a demo and download a plugin that scales the element. The caveat is that you do not get to explicitly choose the target font-size, but, with a little math, you can write a little plugin to convert the target size to a number to scale by.
My personal homepage makes use of this plugin on the welcome page, if you want to see another demo.
Good luck! :)