I saw this a second time today with my daughter, this time she brought a friend.
Enjoyed it more the second time around. On first go, I think I had too much of the book in my head and was constantly checking it against the source material. Second go around I was able to just enjoy it for what it is. Which is pretty damn good.
A few random thoughts and bits that I missed.
I can't remember who it was, but one character watches Bill and company riding in the streets, with Bill yelling, "Hi-ho Silver, away!" without stuttering. I missed it on first go-round, but it was nice to have that in (book reference).
I noticed the librarian in Ben's library scene this time; Bobby and others had mentioned her, but I was focused on Ben and didn't notice on first go. The balloon that drifts by appears where she had been, so it's definitely a manifestation of It. Really effective.
Near the end, when Bowers gets his knife in the mail from It, the other two members of the gang are by Belch's car in the driveway. That's the last time we see the two of them - it cuts to Bowers going to kill his dad inside and they vanish from the film. I think there's a scene cut when he kills the two of them, for a couple reasons. First, he enters the house with the knife out, and it looked bloody already. And second, he's driving Belch's car later on, but the other two are not there. Guessing this gets restored in the extended edition.
I appreciated how Pennywise first noticed the kids no longer fearing him, in the house on Neibolt street. When Bill and Ritchie go through the door properly, It turns around and looks equal measures annoyed, disappointed and curious. As the film goes on that transitions to confusion, anger and eventually fear. Really great performance to capture the slowly changing dynamic.
I swear there was a ~sploosh~ when Bowers hit the bottom of the well. He'll be back.
When we first meet Beverly, in the bathroom, she's got bruises on her arms, just below her wrists. Probably from where her father was holding her arms down.
The cop that stops Bowers from kicking the shit out of Bill early in the film is his father. I didn't make the connection until this time through.