I have opened the back of the case (to access the internal microSD) several times. While it's super simple to open it (just 4 screws hidden behind the rubber "legs"), there are three things to watch for:
1) At least in the prototype units, the battery cable is short enough to accidently stretch and break it if you open the case rapidly
2) When closing the case, extra attention needs to be put into the proper placement of the shoulder buttons, otherwise they might be misplaced and either sink or stick
3) When screwing the case back, be sure not to screw the top row screws too hard, it will cause friction in the shoulder buttons and prevent them from retracting