Yes, another Beatles tribute is on Broadway. Wasn't it just yesterday that 'Rain' opened at the Neil Simon? Pretty much. It was 2010, and Charles Isherwood, reviewing it for The Times, called it 'enhanced karaoke.' In long-ago 1977, 'Beatlemania' - 'not the Beatles, but an incredible simulation' - opened at the Winter Garden and ran for two years. In his review for The Times, John Rockwell decreed it 'an unobjectionable diversion.' Gentle mods and rockers of a certain age, I saw them both. I cringed at the 1977 show. (I mean, all four of the real guys were still alive and in their 30s.) I let myself get carried away at the second. And I can happily report that 'Let It Be' is by far the best of the bunch. The word 'celebration' in the subtitle is well chosen, and the performers are outstanding, as nostalgia substitutes and as musicians in their own right.