The recent additions are
* X(HT)ML parser made incremental, so that it directly handles incoming html fragments and allows to stall when a 'script' tag requires to load a subresource before continuing parsing
* text attributes are made more complete (e.g. 'em', 'tt', 'sub', 'u', 'stike' etc.) - appearance depends on NSTextView's capabilities
* preliminary 'hr' support
For people who do not know the SimpleWebKit vs WebKit issue, there is s thread of discussion.