I have never bought the idea that the second half is in any way inferior..it's just unexpected. For me, the real heart of the piece is found in the second act - The first act is the cerebral half - about making a work of art. The second act shows (those who care about it anyhow)why it matters. I believe that you wouldn't care as much about the first act if there was no second act.
Curiously, people to whom I have shown the video seem to fall in love with the show from that exposure. Yet, many people I meet who first saw the show on stage will complain they found it boring and uninvolving.
I saw it just a few months into the run, having heard the cast album a few times and found it a moving and thrilling theatrical experience. The fact that it provokes such a diverse range of opinions from both reviewers and audience members is to be expected.
What does puzzle me is the hostility it rouses from those who don't like it, as if the fact that others who enjoy the show are "sick" and need to be "cured" of their delusions. You mention that the show won the Pulitzer Prize and they gleefully remind you that it "lost" the Tony Award. You point out that it has had a large number of revivals, and they are only to happy to remind us that the original Broadway run (of 604 performances) was not profitable.
I am reminded of Ethan Mordden's description of the moment in the original staging of COMPANY when at the climax if "Side By Side by Side" Robert has no one complete his dance step. As Mordden relates, people who love theatre were stimulated by it, those who were looking for the standard tired businessman's show were baffled. No only baffled, the growing enthusiasm of the supporters irritated the detractors, who then felt they had to declaim as loudly as possible what a failure the show was. That split has followed not only the Sondheim shows but most contemporary musicals, as anyone who regularly reads BWW will attest.
Cast albums are NOT "soundtracks."
Live theatre does not use a "soundtrack." If it did, it wouldn't be live theatre!
I host a weekly one-hour radio program featuring cast album selections as well as songs by cabaret, jazz and theatre artists. The program, FRONT ROW CENTRE is heard Sundays 9 to 10 am and also Saturdays from 8 to 9 am (eastern times) on www.proudfm.com