There are five main areas that are different:
colors: range changed from 0…255, to 0…1 The v1 compatibility flag fixes.
referencePoints: reference points removed in favor of anchor points, the v1 compatibility flag fixes.
old sprite library deprecated: but it’s been made available on github
:setTextColor change to :setFillColor on display.newText’s.
Objects that were created with an X, Y in the parameters are centered on X, Y, not the Top, Left. I think the v1 compatibility flag fixes that too.
So in theory, the only thing you should have to do using graphicsCompatiblity = 1 in your config.lua is deal with the :setTextColor() and if you’re still using the old sprite system get it from github and include it in your project. Here is a blog post on converting Major Magnet to G2.0:
http://www.coronalabs.com/blog/2013/11/20/tutorial-fast-migration-of-graphics-1-0-based-projects-to-graphics-2-0/