WebKit currently supports CSS Text Level 2.1 version of text-decoration property (link). This version treats only about the decoration line types (underline, overline, line-through and blink - the latter is not supported on WebKit).
The draft version of CSS Text Level 3 upgrades text-decoration (link) property as a shorthand to 3 newly added properties, named text-decoration-line (link), text-decoration-style (link) and text-decoration-color (link), and also adds text-decoration-skip (link) property.
Among other WebKit stuff I've been doing lately, this feature implementation is one of the most cool ones I'm enjoying implementing. I've grabbed the task of implementing all of these CSS3 text-decoration* properties on WebKit, and results are great so far!
As you can see below, these are the new text decoration styles (solid, double, dotted, dashed and wavy - the latter still requires platform support) available:
And also specific text decoration colors can be set:
These features (with exception to text-decoration-skip property) are already implemented on Firefox, thus it gets easier to compare results with different web engines. It is important to notice since CSS3 specification is still in development, all these properties have a -webkit- prefix (ie. -webkit-text-decoration), so text-decoration still maintains CSS2.1 specification requirements. The patches are being reviewed and will soon land upstream, let's hope it will be soon!