I've got a bunch of editing machines, some with CS4, some with CS5.5, and I'm looking to get CS6.
I'm using the demo now, but the sequences and even the transcoded files don't seem to be transferrable to PR CS5.5.
Is there any backward compatibility at all?
I would answer generally yes. There could be some exceptions but in my daily workflow i use CS6 projects on CS5.5. I just have to re-save (with a different filename) the project prior opening with 5.5 (just like when you open for the first time an older project with cs6).
Please note that I'm talking about opening and editing a CS6 project with CS5.5. I don't know what's going in with older versions.
Actually - you can open Premiere Pro CS6 project in Premiere Pro CS5.5
open your project file in any text editor and change -> Version="25" to -> Version="24" (on 4-th row)
After that - you can open it.
Make a copy of your project for backup.
Hope this helps you.