Personally I do not use the screen in performance. Dee Christopher and Nick Locapo have mentioned that they usually do away with it as well. In my opinion, the real strength of the wallet comes from the angle proof handling Dee teaches where the spectator holds the wallet for virtually the entire routine. This does not use the privacy screen at all.
As far as the privacy screen goes, it is easier to get the peek in bright light but it is the angle that makes the screen opaque. The screen will be opaque in dim or very bright light. You will be able to get the peek only if you view the screen directly.