Just tried 3.0 pre-release with our applications. I came across an issue of the 'GraphicsLayer' class no longer having 'units' as an attribute but don't think this change is mentioned in the release note?
Correct, the "units" have been removed (and it wasn't mentioned in the "prerelease" release note). This property was needed for the Map in a few edge cases where it wouldn't get the Units from the metadata of the first layer added to the map. At 3.0, the API is now figuring out the units based on the spatial reference, thus no more need for the "unit". At least that's what we were thinking...
What are you using the GraphicsLayer.units for?
Will it (at 3.0) just work fine if you remove those lines?