It's too bad that so many of us greet the news of another area production of Fiddler on the Roof with an audible groan, because the show itself is really, really good. The music is marvelous, the characters are enjoyable, the story is well-plotted and touching, it's always funnier than you remember it being ... if you're a musical-theatre fan and if you've never seen it, you have no excuse. But, let's face it, it can be a daunting musical to sit through. "I love that show," you'll hear people say, "but, Jesus, it's long ... ."