Awesome work Elijah. :-)
I think if you have 'float: left' or 'float: right' elements inside a container element, the container (in standards browsers) has no height, resulting in losing backgrounds, and it's normal block level behaviour. This is the opposite in IE, ironically.
I've already compiled a small list of issues, separate of the Optimal Usability guide that we can probably accomplish. However, that guide in itself does outline a large portion of work to be done.
I'll be in touch next week,
Cheers,
Sean