Latest Iceweasel 11 user agents:

User Agent Platform Device
Mozilla/5.0 (X11; Linux x86_64; rv:11.0a2) Gecko/20111230 Firefox/11.0a2 Iceweasel/11.0a2 GNU/Linux Unknown
Mozilla/5.0 (X11; Linux i686; rv:11.0) Gecko/20100101 Firefox/11.0 Iceweasel/11.0 GNU/Linux Unknown
Mozilla/5.0 (X11; Gentoo Linux x86_64; rv:11.0a2) Gecko/20111230 Firefox/11.0a2 Iceweasel/11.0a2 Gentoo Unknown