Kernel:
Stable - 2.6
Testing - 3.2
Unstable - 3.2 (released July, 2012)
Current version - 3.8
Those 3.6/3.7 files seen in your link? Experimental. Yeah you could make it work, but then you aren't running Sid anymore. Not entirely. And if you run too much experimental for too long, something is going to end up horribly broken.
Firefox/Iceweasel:
Stable - 3.5
Testing - 10esr
Unstable - 10esr (released March 2012)
Current Version - 19.0
Libreoffice:
Stable - 3.5
Testing - 3.5
Unstable - 3.5 (released February 2012)
Current version - 4.0
YOU DO have very recent packages available, even right now, during the freeze of testing. I haven't checked DE and X, since I don't know what you run (eg: which graphic card, and which environment you like).
I run XFCE on testing, not that it matters.
XFCE:
Stable - 4.6
Testing - 4.8
Unstable - 4.8 (released Jan 2011)
Current Version - 4.10 (released April 2012)
Like I said, Sid isn't bleeding edge. Of the packages here, the newest in Sid is the kernel: 7 months old.
It's also worth noting that drivers receive unblock from the release team so that they can enter stable.
Well that's great (and I genuinely mean that), but a bleeding-edge enthusiast would only see that 3.2 != 3.8.