just saw it tonight and seconding that this is just act 1, so there are a lot of hanging threads and spoilers may be abundant because the show's been running for 20+ years if you're going to look into convo about it. otherwise, there are little things here and there that definitely are fun easter eggs if you know the show/Wizard of Oz lore
but also I saw it tonight with a friend who's also deeeep in Wicked/Wizard of Oz lore and another friend whose only heard a few songs from the musical and hasn't seen WoO in years and she had a blast