The IE9 Platform Preview isn't a beta release of the next Internet Explorer browser; in many ways it's not a full browser and you certainly wouldn't want to use it for your day to day browsing (and Microsoft doesn't want you to). There's no address bar, no back button, no tabs, no favourites, no error messages if pages don't load and none of the usual browser tools, including no malware protection. All you get is a minimal window around the IE runtime and some simple menu options for reporting bugs, running developer tools and forcing windows to load as if they were in older versions of IE. There are improved versions of the developer tools with support for SVG; there's a network tab that shows you what network traffic is generated by the page — a powerful tool for seeing how fast your site will load and when it's going back to the server for things that you might be able to shift to running on the browser.
The IE 9 developer tools
That's because the preview isn't just a way to show users that IE9 is going to be faster and that it's going to deliver standards-compliant HTML 5, CSS 3 and SVG; it also gives Web developers a chance to see what their own sites will look like in IE9 and how that changes from previous versions. The demos on the Test Drive home page are also there to inspire developers to think about what they could build into HTML 5 apps and sites.
Navigating within the preview is perhaps deliberately awkward; Ctrl-O or Page > Open brings up a dialogue where you can type in a URL, pick a page you've visited previously from the dropdown or open a file from your system. F10 takes you back to the main Test Drive page (or gain you can navigate from the Page menu). You can't print directly — although you can see a print preview to check how that renders and if you really need to you can print from there.
You can load pages in IE9, but it's not a full browser interface
If you're a developer wanting to see the future of IE, then this is an essential download. It installs side-by-side with IE8, so there's no conflict with your existing browser. A promised update every eight weeks will also keep you up to date with APIs and tags as they're added, and also with changes resulting from the evolution of the HTML 5 specification. How the final browser will look is anyone's guess — all IE general manager Dean Hachamovitch will say today is that it will be an 'interoperable HTML 5, hardware-accelerated, high-performance browser'.