And you still haven't defined "fail".
If he uses the same definition that the pre-launch iPad critics used when they were saying the iPad would fail, if it doesn't ultimately become the top selling tablet device, then it has failed.
Applied to either product, that view isn't very realistic.
Based on the specs and the OS, I'll be surprised if using the Slate will be as nice as using the iPad. An Android tablet makes far more sense than this does.