Mozilla is ahead of schedule with Firefox 5 and have decided to release it early. It will be released "officially" on June 21st. Firefox 5 doesn't include any GUI changes with the design interface remaining identical to Firefox 4. Most plugins should have no issue working with the new version.
The latest stable version is said to offer more stability and improvements than the former test builds. For some download links depending on your OS, I've included them below:
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