(This post will be edited to reflect the current list. Feel free to post if you think this list needs to be edited.)
Planned/Completed Features For Tablet 83:
-Buttons and text-input in GUI (Partially done)
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-All operations in 83+
-History support
-function definition in home screen
-TabletPC specific GUI

Features that will be considered eventually:
-Support for 83 programs
-Program Editor
-Auto-indent in program editor

Features that float through my head but may or may not be considered as an option:
-some form of symbol manipulator
-Dynamic geometry editor in graph screen
-3-D Graphing (strictly graphing)
-TI-89 commands
-Support for 89 programs