The Lightroom 4 beta program is available to the public. Anyone with an Internet connection can download it and start putting it to the test. You do not need to own (or have tried) a previous version of Lightroom. You can download the beta and use it until the product expires on March 31, 2012.
"The Lightroom 4 beta program is available to the public. Anyone with an Internet connection can download it and start putting it to the test. You do not need to own (or have tried) a previous version of Lightroom. You can download the beta and use it until the product expires on March 31, 2012."

http://labs.adobe.com/technologies/lightroom4/0