Wow, I wouldn't touch that type of update until it was at least 2 minor updates later. With that many fixes there's bound to be more (possible severe) security bugs introduced.
Not in this case. Mozilla's sealed more security holes than the tech press knows exists. There were a few nightly builds where five or six security holes would be sealed all at once. The major problems with new Firefox builds are the regression bugs, but they solve those before general releases. Still waiting on them to fix a nasty focus bug related to the find-as-you-type feature, though: it was marked as fixed before, but seems to have regressed.