The musical was quite good, especially in the first act. It needed some focusing in the second act, but the overall evening was impressive. The songs were written to the show and the characters, not as "Barry Manilow hits." For years Manilow wouldn't even sing any of them in his concerts -- in part, because they weren't really standalone songs for the most part, but "book songs." Only one, the terrific "Every Single Day" (linked above) did he finally put into his repertoire.
As I noted a few months ago, "pre-Broadway" of 16 years took on new meaning when the highly-regarded Alliance Theatre in Atlanta has teamed up with the Center Theatre Group in Los Angeles and are finally mounting Harmony once again, with hopes on a Broadway production. (Alliance has premiered such Tony-winners as the musical The Color Purple, Aida by Elton John and Tim Rice, and Alfred Uhry's The Last Night of Ballyhoo. Uhry is the playwright of Driving Miss Daisy.)
And it opens at the Alliance this coming Friday, September 6. (Los Angeles gets the show at the Ahmanson in March.)
Here's an interview that Manilow and Sussman did with the Today Show about the long journey with their show.