Latest Firefox 4 user agents:

User Agent Platform Device
Mozilla/5.0 (X11; Linux i686; rv:1.9.6.20) Gecko/ Firefox/4.0 GNU/Linux Unknown
Mozilla/5.0 (Windows; U; Windows NT 6.1; en-US; rv:2.0b10) Gecko/20110126 Firefox/4.0b10 Windows 7 Unknown
Mozilla/5.0 (Macintosh; U; PPC Mac OS X 10_11_4; rv:1.9.2.20) Gecko/9899-10-22 15:17:45.697205 Firefox/4.0 Mac 10 Unknown
Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:2.0.1) Gecko/20110606 Firefox/4.0.1 Windows XP Unknown
Mozilla/5.0 (X11; Linux x86_64; rv:2.0.1) Gecko/20110506 Firefox/4.0.1 GNU/Linux Unknown
Mozilla/5.0 (Windows NT 5.1; rv:2.0b13pre) Gecko/20110223 Firefox/4.0b13pre Windows XP Unknown
Mozilla/5.0 (X11; U; Linux i686; ru; rv:1.9.1.3) Gecko/20091020 Ubuntu/10.04 (lucid) Firefox/4.0.1 Ubuntu 10 Unknown
Mozilla/4.0 (compatible; Intel Mac OS X 10.6; rv:2.0b8) Gecko/20100101 Firefox/4.0b8) Mac 10 Unknown
Mozilla/5.0 (X11; Linux x86_64; rv:1.9.6.20) Gecko/8578-02-25 03:39:20.183105 Firefox/4.0 GNU/Linux Unknown
Opera/4.0 (Macintosh 3.1; rv:2.0.1) Gecko/20100101 Firefox/4.2.1 Mac Unknown
Opera/4.0 (Macintosh 3.0; rv:2.0.1) Gecko/20100101 Firefox/4.0.3 Mac Unknown
Opera/3.0 (X11; Linux x86_64 4.0; rv:2.0.1) Gecko/20100101 Firefox/4.3.3 GNU/Linux Unknown
Opera/3.0 (X11; Linux x86_64 3.1; rv:2.0.1) Gecko/20100101 Firefox/4.0.1 GNU/Linux Unknown
Opera/3.0 (X11; Linux x86_64 3.0; rv:2.0.1) Gecko/20100101 Firefox/4.0.1 GNU/Linux Unknown
Opera/3.0 (Macintosh 4.1; rv:2.0.1) Gecko/20100101 Firefox/4.0.1 Mac Unknown
Opera/3.0 (Macintosh 3.0; rv:2.0.1) Gecko/20100101 Firefox/4.4.1 Mac Unknown
Mozilla/5.0 (X11; U; Linux i686; en-GB; rv:2.0) Gecko/20110404 Fedora/16-dev Firefox/4.0 Fedora 16 Unknown
Mozilla/5.0 (X11; Linux; rv:2.0.1) Gecko/20100101 Firefox/4.2.33re GNU/Linux Unknown
Mozilla/5.0 (X11; Linux x86_64; rv:2.2a1pre) Gecko/20110324 Firefox/4.2a1pre GNU/Linux Unknown
Mozilla/5.0 (X11; Linux x86_64; en; rv:2.0) Gecko/20100101 Firefox/4.0 GNU/Linux Unknown