Warning: SPOILERS under the cut.
First, I loved the creatures! I think everyone did, there was a lot of laughter. I especially loved the niffler.
I also found the different in graphics striking; I was surprised at how different House Elves looked, then I realized: "aha, 2016 technology versus 2002 technology." And actually, IIRC Kreacher looked close to those House Elves as well.
Now, onto what I thought about the story.
When the sixth Harry Poter book came out, my reaction (apart from being giddy over the Remus/Tonks) was pretty much "hum. Interesting." And then, "I think I have to read Deathly Hallows to really appreciate this one."
That's pretty much my consensus here. I LIKED it enough, but it didn't leave me with my head spinning. Mostly with a desire to read fanfic (and maybe write some of my own fanfic) that may or may not expand a little on the movie's themes. I know there'll be more, and I hope when there is I'll be able to go back and appreciate the first one (the way I actually really like The Half-Blood Prince now), but for the time being I just don't really know... what to think.
The difference with HBP and Fantastic Beasts is, of course, that we already knew the characters and the basic premise. Here, we really don't, and I never felt engaged enough with them. I liked Jacob and Queenie, although I still had to ask my cousin what her name was afterwards, and we scrambled our brains a bit before landing on "Queenie."
Newt... I felt like he should have been way more lovable than he was. I'd read in other responses that he was, so maybe it was just me raising the bar too high, but I didn't really feel that strongly about his character. I think he has potential to become very cool future films, though; the same can be said for Tina. I think the movie was too busy with magical creatures to really add depth to their characters, and I do hope that future ones give them nuance. The fact that Newt was in love with a Lestrange(!!!) is a start.
I found the American wizarding world interesting. They're definitely less tolerant of wizards and witches; dangerously close to Voldemort, really, although it was always implied the UK wasn't much better, just... better at hiding it. (Plus, this was when America had segregation, so perhaps there's also a parallel there as well.)
So... there you have it. Is there going to be a novelization, or is it just a script like The Cursed Child? Because I think a novelization could add a lot. In the meantime, I'll satisfy myself with fanfic. Because like I said, I DO think the movie had potential - it just didn't quite get there. Hopefully future films will be more satisfying.