Something tells me Jun is being intentionally vague.
But since it doesn't say "how important is YOUR faith" I will interpret it as faith in what I am practicing.
The only faith I have is that if I keep training, certain things will be revealed to me. But that's faith based on experience which to me is really trust. I only trust based on history. I'm from the "show and prove" school. Prove it and I'll believe it. So in a general sense I have faith in the value of aikido training based on experience. Regarding individual aspects or interpretations of the art that I have not yet experienced or mastered, time will tell.