First of all, as I was watching the opening scenes of the characters preparing for the party and Donald parking his car in a lot, I realized this was a filming of Mart Crawley's screenplay for the 1970 movie and not an adaptation of the Broadway script.
Firstly, this was a WAYYY better acted, designed and directed version of BITB than what conspired on Broadway with the same cast a few years ago. Zachary Quinto was a faded xerox of Leonard Frey's original Harold, Jim Parsons was strained and flat as Michael with no searing emotional highs or lows. I agreed with the poster above who said that Parsons is a character actor and Michael needs a leading man or dramatic male lead. Well, Quinto really went toe to toe with Frey in the filmed version and though Parsons didn't have the demonic glint in his eye at Kenneth Nelson had in the movie when Michael gets mean, they both convinced me.
Matt Bomer was bland onstage and faded away when Donald isn't speaking which is most of the time. Here, Mantello was obviously taken with his beauty and gave him lots of reaction shots and close-ups which kept Donald in the picture in Act 2. Bomer has more screen presence than stage presence. I found Rannells very glib and posey onstage - he registered more strongly in the film with less mannerisms.
Wonderful on Broadway and perfect in his role, Tuc Watkins as Hank and his performance was equally wonderful on the film. Watkins should do more Broadway. Robin De Jesus I thought was a better Emory than Cliff Gorman was in the movie (Gorman and Laurence Luckinbill were the only straight actors in the original cast). He basically stole every scene onstage. The movie made Emory more part of the ensemble and dampened some of De Jesus' bravura.
Reuben Green was so mysterious and sexy leading man as Bernard in the original film - he pretty much disappeared and no one knows much about him. Michael Benjamin Washington was more of an ordinary shy guy which I think is a better fit for Bernard who is kind of a bystander in life.
Brian Hutchison really registered so powerfully in the Netflix film - he didn't make much of an impression onstage and he was overwhelming here.
Also, on Broadway there was this two-level purple Barbie Dream House penthouse with velveteen walls and also sort of silver chrome and mirrors. It was an eyesore. Following the movie, Michael's apartment is much more bohemian and run down chic with that balcony. It is very similar to Tammy Grimes' apartment that was used in the 1970 movie.
I agree there was enough humor in the first half of the play as R94 said. Parsons is mostly known as a comic actor and he could have scored here but played fairly depressed and neurotic in his initial scenes.
I have always had a lot of older gay male friends decades older than myself who are the same generation as the characters in this play. The self-loathing and bitterness can be very real with them. When Michael says in the last scene "If we could just learn not to hate ourselves quite so very much." it is a plea to his generation to have more self-worth and bravery. That attitude led to the Stonewall Riots in the summer of 1969. This play in its way was pushing gay men past this self-pity and self-destruction - Crawley was making a diagnosis and not supporting the internalized homophobia.
These men also cling together because of society's rejection of them - Mantello's production did capture the pain and feeling of rejection these men share.
I've always liked this play. But it is a snapshot of its time. It points out problems Crawley saw in himself and his community. Gay men still treat themselves badly and fuck up to punish themselves. They still abuse drugs and each other. They still kill themselves. So it isn't like we are all perfect.
This was a stronger ensemble onscreen than it was onstage and there is lots of strong writing and witty humor to be savored. I was glad I saw it.