The latest one for Debian updated Iceweasel to 31.2.0, and my toolbars went away.
I managed to get the menu bar back, but the bottom bar (status, and where several addons park their icons) is gone, and the look & feel of the top bar have changed drastically.
I don't like unsolicited UI changes. I really don't like having them dragged in by security updates.
Gotta get switched to some other browser. (Ability to print to a Postscript printer from Mozilla-derived programs has been deteriorating of late, too; I haven't tried printing from this new thing yet.)
Update: Seems the bottom status bar had gone bye-bye long ago, and I'd brought it back with an add-on called Status-4-Evar, which has now ceased to do its thing. Also, some stuff that used to be in the top location/status/tool bar has disappeared, and some stuff that used to be at the bottom has moved up there. Like the link preview... which is now a whopping inch wide, and shows, roughly speaking, "http://....html", which is not very informative.
Update 2: Turns out I had an older version of Status-4-Evar installed, and the current one wasn't turning up on a search of "Get Add-ons", let alone updating automatically. Googling for it found its page, and a fresh install resulted in it getting updated and working again.