Because of the new development schedule, Firefox 5 comes just 12 weeks after the release of Firefox 4. The new release schedule also means that, unlike the earlier major releases of Firefox, Firefox 5 is not drastically different from Firefox 4.
To get Firefox 5 now, you can download and install the beta from here. After installing the beta, update it from Help > About Firefox.
(Note: You might want to read this article, if you want to install using the PPA in Ubuntu.)
Here are some benchmark scores for Firefox 5:
- SunSpider 0.9.1 – 342.0 ms
- V8 Benchmark – 2186
- HTML5 Test – 255(+9)/400
We will publish a more detailed benchmark with comparisons between different browsers and operating systems later.