I can report that firmware flashing worked without a problem.
According to the release notes there is no functional difference between the new (beta) and old drivers other than the signatures and changes to the installer. I think the challenges with power saving due to differences with 10.10 and older versions. Apple changed the kernel a lot with 10.10 and unfortunately some was not for the better.
I could not install the previous version due to those versions not being signed. For security reasons I don't want to put my Mac in developer mode as recommended by some as that weakens the kernel security substantially.