Anyone can download this build which is available in both 32-bit and 64-bit version but be warned that this is early pre-released version of Windows 8 which might not be stable or might not operate correctly. Microsoft’s official website reads:
The Windows Developer Preview is a pre-beta version of Windows 8 for developers. These downloads include pre-release software that may change without notice. The software is provided as is, and you bear the risk of using it. It may not be stable, operate correctly or work the way the final version of the software will. It should not be used in a production environment. The features and functionality in the pre-release software may not appear in the final version. Some product features and functionality may require advanced or additional hardware, or installation of other software.
Since the requirement of Windows 8 are same as of Windows 7, you can go ahead and try Windows 8 build if you are running Windows 7 with no stability or performance issues. The requirements are 1 GHZ Processor, 1 GB of RAM, 16 GB of free HDD space and a DirectX 9 graphics card with WDDM 1.0 or higher driver.
I haven’t tried this yet on my computer so I’m unable to provide any experience on this. Why don’t you try this out?