The Omni Group has released OmniWeb 5.5 beta 1 which is now based on a slightly customized version of WebKit. This means greatly improved website compatibility, speed and stability, accroding to the developer. Many rendering and compatibility issues users have been experiencing should now be addressed.
New Features and interface improvements:
• OmniWeb is now a Universal Binary
• OmniWeb now supports saving in the WebArchive format via the “Save As…” panel.
• There is now a global and site preference for user defined style sheets in the Appearance pane.
• Toolbars in OmniWeb now use the Unified Toolbar.
• A warning will now appear when you try reloading a page using POST. When loading a workspace containing POST pages, the page will display an error but can be reloaded to rerequest the page.
More info and download link here.