It's firefox. With no firefox logos.
That's it.
Granted, the releases are behind firefox, but that's debian.
Debian has a strict rules on proprietary software and as such all code in the standard Debian repositorys all must be GPL or some other FOSS license such as the BSD. Mozilla refused to GPL their logos and such, so Debian took the rest of the code, and re-branded it and repacked it.
Also, it's not Mozilla Iceweasel. The code is Mozilla, but it's not maintained by them. It's maintained by someone on the Debian team last time I checked.
So, pointless thread is pointless. It's just firefox with different logos, and a much slower release schedule.
Other than the fact that it's ridiculously slow on my Atom netbook (both Chromium and Epiphany run fine, serious), it's fantastic. Except for the name. The name is awful.
I'll refrain from posting yet another picture of an animal humping a blue ball though.