Firefox 64 bit for Windows?

Firefox 64 bit for Windows is the plan of Mozilla. It’s one of the Firefox 4 features.
Programmer Armen Zambrano Gasparnian announced the first 64-bit Firefox builds for Windows on Friday, offering an FTP site for those who want to download it. But the software isn’t for mainstream users yet.
The transition to 64-bit computing often offers a modest computing performance boost, but the main reason for the transition is getting around the 4GB memory limit of 32-bit computing.
Apple’s Safari and Microsoft’s Internet Explorer already have their 64 bit versions. Google is working on 64-bit Chrome too.
This software only function in 64 bits platform(windows 64 bits or windows vista)