I just landed a changeset that changes the names of the layer acceleration prefs in Firefox.
The old prefs were:
The new prefs are:
layers.accelerate-all previously defaulted to 'true' on Windows and OS X. Which meant that there was no easy way to force layer acceleration on if your card had been blacklisted for some reason. The new prefs allow the blacklist to be overwritten. The old prefs are not being migrated over to the new names. If you have a problem with the defaults, please file bugs.