Compatability View is a toggle button that appears on the toolbar when some elements of a Web site don't render properly. It automatically forces a change of rendering engine from IE 8 to IE 7 to keep the page looking as it should.
Here, you can see that although Microsoft's own home page views correctly, Google.com and even Download.com both get the Compatibility View treatment as indicated by the presence of the broken-page icon.
One of the new features in the Release Candidate that wasn't in IE 8 beta 2 was the ability to tailor the Compatibility View list to your requirements. Users can configure all pages to render with the older engine, turn it off completely, or force-add sites on their own.
Internet Explorer 8 brings InPrivate browsing to IE fans. This feature became the must-have feature of 2008, as Firefox, Google Chrome, and others made hay of its introduction--even though the technology is old. Like its competitors, InPrivate turns off memory caching, cookie saving, and other Web surfing traces that can be left on your computer.
This small but useful change in the release candidate brings InPrivate's filtering list into the regular, cache-and-cookie activated Internet Explorer. It's an added measure of security, in theory, but in practice it's a bit hard to define what effect it actually has.
The Web Slice add-on for the site that you're interested in "slicing" must be installed before you can choose to activate it. Clicking the green button that appears after a site-specific Web Slice has been activated lets you configure the sliced information, but since users have to navigate to a Microsoft page to activate the feature in the first place, it's an awkward workflow.
The Web Slice for Live Traffic struck me as a great idea, but the execution of it is lacking. Being able to receive real-time traffic updates to a bookmark is fine, but when the map that appears requires another click to drill down to more detailed information, you know that there's more that could be done with this.