I am not seeing any major modifications in these updates, and i found annoying to be advice so often to update firefox.
Try running it from some Linux distros. Mint 12 still happily proclaims that Firefox 3.6 is the "latest version" using the package manager, and the only way to get 8.0 was the build the bloody thing from source. Not something I care to repeat so at 8.0 I stay.
Most of the changes seem to be in the area of HTML5 support. At least that would be my guess.
the BIGGEST... and I mean absolute biggest problem with Firefox has to do with two things.
C++ and Garbage Collection.
C++? Fine. Garbage Collection? Fine. But the nature of the two beasts makes them pretty much incompatible. having to restart Firefox because it's laden with that leftover garbage and sitting at 1.5GB of RAM with a single tab open is downright ridiculous.