If you use Firefox and want to see if this new tag is getting used, add something like this to your userContent.css file:
a[rel="nofollow"]
{
text-decoration: line-through ! important;
border: dotted thin gray ! important;
color: gray ! important;
background-color: white;
}
This will put a strike-through and a dotted border around the link text, and make the text gray with a white background.
Nice! 