The new version does not have in visual changes but it does bring some improvements under the hood.
Improvements in Firefox 5.0
- Firefox channel switcher;
- Location-Aware Browsing;
- Support for CSS animations;
- Increased discoverability by using the Do-Not-Track header preference;
- Improved canvas;
- Improved memory usage;
- Improved networking performance;
- Better spell checking;
- Better desktop environment integration;
- Better standards support for HTML5, MathML, SMIL, canvas, and XHR;
- Improved performance for background tabs;
- Overall performance and stability enhancements.
Although the files are not available for download from Firefox website or from the Ubuntu official repositories, sites like softpedia.com and downloadcrew.com already have them in their repositories. To download from softpedia, please follow the link here. Both 32 and 64bit binaries are available for download.
Link from download crew can be found here.
So go ahead and grab your copy!
Update: Firefox 5.0 is now available at the Firefox webpage and for Ubuntu users it is available in the Ubuntu proposed updates repository.