In order to avoid problems with Add-on compatibility——-> Download Add-on Compatibility Reporter
Firefox 3.6 version is faster and more responsive than previous versions and has been optimized to run on small device operating systems such as Windows CE and Maemo.
There are more than 70 fixes from the last beta to improve performance, stability, security and features.
And 3.6 version is compatible with Windows, Linux and Mac OS X in more than 70 languages.
Know issues———> Click Here
Read More: Download Firefox 3.6 RC