[css3-ui] "nav-*" properties have <id> selector as value.

Hi www-style,

I'm Kyounga Ra, want to hear your opinion on a "nav-*" properties.
(http://dev.w3.org/csswg/css3-ui/#nav-dir)

When I was trying to develop these css3 properties (nav-*) on WebKit project, other developers told me that it looks odd or unstable. 
Because, no other CSS property has bare selectors as value. 

It has been suggested that I hold off implementing this until CSS WG has had a chance to discuss this further. 

So, I'm writing this email to you, www-style.
Are these properties stable or valuable as a standards?
Opera browser already is supporting this.

I'd like to ask you discuss on this issue.

Warm Regards,
Kyounga.