I'm really interested in seeing whether they will change the Mind Flayer's Mind Blast design. Stunning players feels so bad, especially when you're fighting multiple enemies with that ability.
I hope they will do something like they did with the Empyrean where you can choose to take additional...
One thing I don't like about the Kobold Press monster books is how the stat blocks seamlessly spill over multiple pages (even across spreads). It makes it hard to read the whole stat block at the same time and is something that WotC manages to avoid with conscious layout choices.