I've got several AR apps in development using older versions of Vuforia. I don't need either user-defined targets or cloud recognition for these apps, so I'm not sure if I should update.
Are there any performance improvements that were made to 2.0?
The release notes list a very vague feature, "Improved tracking robustness." What exactly is meant by that?
The 2.0 tracker is better able to maintain stable augmentations when there is relative movement of the target a/o camera. It's also less affected by occlusion and better able to exploit the features of the target. So generally your augmentations will be more stable under a broader range of conditions and use cases.
If recommend testing 2.0 w/ one of your existing apps to see whether these improvements will be beneficial. You'll want to review the migration guide for you SDK before you do though - https://developer.vuforia.com/search/apachesolr_search/migration