The only time you should use a "creative" interface is when absolutely no other standard interface pattern is available. Otherwise you're throwing away a great deal of learned behaviour in your users and forcing them to consciously hunt for what they want instead of relying on common patterns.
I think Bootstrap is wonderful to allow you to start hacking away on an app and have it look halfway decent through that process. But I agree that once it moves on to a beta stage more focus should be placed on a unique / better design.
