Yes, a given, when you save backwards you loose new features. And as in Illustrator, when you save backward you get a warning. And in 95% of cases it's not going to affect the work.
I disagree rapid development precludes backward compatibility. Until CC 2014 it didn't for After Effects, Flash, In Design, Dreamweaver Photoshop and the list goes on. I believe this is a conscious omission on the part of Adobe and we as the consumers should not just accept it but demand this feature be reinstated. And in the case of Premier, added. Again if you can XML it, Adobe can add a Save As. You can't XML an AEP.
This is not just for students and educators. I see this need for anyone who needs to be mobile and working in multiple environments and not necessarily with their own equipment. That's a lot of users. Remember, a key point of the subscription model according to Marketing is mobility.
So even if you only see it useful for mere students, I ask you to join me in requesting this from Adobe.
BTW - If the installer can't keep up - thats a concern don't you think? Maybe things should slow down a bit to avoid an IOS 8.1 type screw up.