So the first preview - anticipation from the whole audience was super high, excitement in the room, much applause. The show started rather late and intermission ran late as well. Loads of folks trying to buy merch - I see pics have been posted already.
I really enjoyed Josh Groban in The Great Comet and had high expectations for his Sweeney. He was in fine voice and for those worried that his vocal range was not suited to the part - well, we thought he sang it beautifully! I felt his acting was much more muted in act one than I expected. I think he was going for Sweeney's slow transition from arriving bitter but with some hope in London at the start to the great transformation into revenge driven Sweeney by Epiphany, but I would like to see him ramp up the anger more to be even more frightening. And more blood needed - we got some in act one, but none when the Judge meets his demise? We'd've liked more physical struggle and seeing Pirelli's end as well. Josh and Annaleigh are definitely playing the roles younger and more playfully in parts. More overt flirting from her, with disinterest from him until they really make their deal. A Little Priest was just fantastic, the most enjoyable version I've seen, and the two of them had great fun with it! But I hope Josh Groban develops an even angrier, darker Sweeney as the run continues. He nailed it during Epiphany - just would like to see more hints of that earlier in the first act.
Annaleigh Ashford was an absolute delight - the funniest Mrs. Lovett yet, and I'd not be surprised to see her get Best Actress in a Musical for her work. That being said, there were moments when the unrelenting humor of Lovett sort of undercut Sweeney's menace. In act two, as the play wended towards its conclusion, more fear from Lovett towards Sweeney would have packed a bigger punch at the end. The scene of her demise was fine, but as others have noted, could have even more struggle and turmoil and horror to it. One moment that struck us as perfect was the anger in her voice when she tells Sweeney at the end "I'd be twice the wife she was!" Great delivery!
I'm not getting all the negativity towards Jordan Fisher?! We really liked him in the role! I admit that Anthony has never been a part I enjoyed in the past - but other than a wavering accent, we thought Jordan was charming, engaging and sang wonderfully in this. Definitely did not see him as the "weak link" in this cast! If anything, we were less enthralled with Joanna - beautiful singing voice who hit those incredibly difficult notes perfectly, but more muted in the acting department.
Gaten was terrific. I am only slightly familiar with his work in Stranger Things, but he performed beautifully in every scene. He was funny and lively with Pirelli's elixir, and moving with each scene he had with Lovett. Really a strong performance. Also, we LOVED Pirelli! Oh my goodness, he was funny, beautiful voice, and though his Irish accent wavered a bit later in the play, his number was one of the highlights of the show. Beadle Bamford was very good, strong performance, but we were sad to see the Judge's number cut. The judge was suitable creepy, but I admit to wishing Patrick Page had been available to give that part a go...
Also, perhaps due to our being further back in the audience, it looked like the cleanest London we'd ever seen compared to other productions. We expected more than just the beggar woman to look somewhat scruffy. An even darker and dirtier London please! Ensemble was fine, but would somebody also put Timothy Hughes in another big dance show please where we can see his incredible moves? 
That ending moment of the show with Sweeney and Lovett - unexpected but a wonderful closing. The audience was thrilled. We were too. I expect this show will only get better and better during the run. Go see it.