There is not much being said outside of Germany about YAML, and, me being out of the loop just got aware of it recently, too, but I must say that if you are looking for a well-documented CSS framework and the YUI grids do not to cover what you try to achieve, YAML is worth a closer look. It is amazingly well documented in German and the maintainers put a lot of effort into creating the English version of YAML for the rest of the world to understand more easily.
Probably the biggest boost you can give any CSS framework is take the initial pain of creating the HTML with the correct classes and IDs away by creating a WYSIWYG editor and the YAML folks have done this with the YAML builder also based on jQuery.
YAML is a product worth keeping your eye on as the maintainers are eager to extend and maintain it and take on interesting feedback to add improvements to the next release. It is furthermore quite lucky that the product is targeted to a much different audience than hardcore developers as the clash with the straightforward machine parsable data serialization format with the same name could be confusing.