EDIT: (Nov 2, 2013) All issues reported in this old post have been fixed.
I've taken one of my published apps and converted it to Graphics 2.0 (as far as is currently possible).
Apart for some issues (more on that later), I've gotten it functional.
Most of the work that needed to be done came down to 2 things:
1) Changing setReferencePoint to object.anchorX and object.anchorY
2) Deciding which display-groups to leave as-is or convert to containers/snapshots
The deprecated sprite.* API is gone, so you'll need to use the new API if you aren't already doing that.
ISSUES in Graphics 2.0:
1) No support for the newer table style params for newText 2) Can't rotate stage around center of screen (see comments below) 3) Line objects do not accept image strokes
Objects that are not visible do not receive events even though isHitTestable is set to true 5) Physics objects do not take anchor point into consideration (affects collision detection)
(All of the above issues have separate threads in this forum section)
No device testing has been done as it's not functional in the current build, so testing has only been done in the Corona Simulator.
I've also noticed rendering issues with some containers that are nested within multiple display groups. Some (not all) containers fail to crop their contents within the bounds. I've tried to write a test-case for this issue, but it behaves as expected when doing so, which means I've stumbled upon some edge-case in my production code. I'll keep monitoring this issue in later builds...