The Windows 8 Release Preview ISO file is an image of the latest Windows 8 setup disc, which will make it quick and easy to install the operating system on the hardware of your choice.
Please note that this is the feature complete version of Windows 8 and is a very good example of what you'll see in the final build later this year,
The safest option, then, is to install the Release Preview on a virtualisation tool, such as VirtualBox. Performance won't be as good, but the convenience of running Windows 8 in a window on your current desktop will more than make up for that with most people.
Installation itself is generally straightforward, much as you might expect with any other version of Windows. And (if you don't take our virtualisation advice) the operating system should install on any hardware which can run Windows 7. The only complication is that you'll need a product key: the Microsoft Windows 8 Release Preview FAQ says everyone can use TK8TP-9JN6P-7X7WW-RFFTV-B7QPF.
And once setup is complete then you'll be able to explore the many improvements in Windows 8 Release Preview. The Start screen is more configurable and easier to use; it's easy to pin and group apps and shortcuts for speedy access; Search is smarter; there are many Metro apps; and the Windows App Store is now available with plenty more to browse and download. Go take a look for yourself.
Verdict to follow.