I was there last night and liked it, but didn't love it - and I went in wanting to love it, so I can't help but feel a bit let down. I don't have much to add that hasn't been said here already, but here are a few thoughts.
The omission of the factory whistle is a huge, huge misstep. I missed it at so many points throughout the night - at the very top of the show, throughout "City on Fire," during many of the killings. It does so much to help set the tone of the show, and there were many moments that would have packed more of a punch had the whistle been present.
I also left last night finding myself in the "more blood" camp; I liked the blood during the Act II "Johanna" sequence and would have liked to have seen more throughout. There was a bit during the final killings, but I really felt like they could have gone further. Between the whistle and the blood, it seemed like this production was stepping away from the "thriller" part of "A Musical Thriller," and I wish they had leaned into that a bit more.
I really enjoyed both leads, and was especially impressed with how Ashford balanced humor with some of the quieter, more emotional moments of Mrs. Lovett. I thought Ruthie Ann Miles was absolutely phenomenal as the Beggar Woman, and, if it were up to me, she'd be nominated for a Tony in a few months for her performance. She builds a complete, complex character, even with limited stage time; there are shades of the Lucy she once was from her very first scene, making her circumstances all the more tragic.
While I wish the set had taken a bit more inspiration from the original designs, I thought it was effective in both its design and aesthetic, and I particularly enjoyed when the bridge tilted during "City on Fire," creating a stage picture that (from the mezzanine, at least) really reflected the text. I also enjoyed the final moments of each act, particularly the second, and I imagine that would have played even better had I been sitting in the orchestra.
As for the music: the 26-piece orchestra was my biggest selling point for this production, and, unfortunately, it didn't deliver the way I had hoped. I agree with others here that the orchestra sounded distant; this is perhaps just a sound design issue, and one that can hopefully be worked out as previews continue. But from where I was sitting, the music just didn't fill the space. The OBCR is pretty much the only recording of Sweeney that I listen to, and it's largely because of the orchestrations. I was so excited to hear them finally played in a Broadway theater, but, last night, they never sounded quite as full as I wanted them to.
I feel like I've mostly listed my gripes here, which is making me come across harsher than I mean to. Like I said at the top of my post - I liked the production, it just didn't blow me away the way I was hoping. I would consider revisiting it at some point in the future, likely after opening - hopefully by then they'll have been able to work out any sound design issues and will have (pretty, pretty please!) added in the whistle. Those two things alone may be enough to completely win me over.