Nothing I really ban but there is a bunch to be aware of.
1. Druids and clerics are very strong classes, particularly compared to older editions.
2. Rogues do a lot of damage, this is their job.
3. Save or X spells are usually very potent.
4. Wizards can be very effective at battlefield control.
5. At higher levels scry, buff, teleport is a common tactic.
6. Flying magic becomes common at middle levels and teleport at a little higher.
7. Boosting spells pile up, recalculating everything after dispel magics is a chore.
8. Even though you can, you don't need to stat out monsters/NPCs fully, its ok to assign skill stuff on the fly and only as needed, etc.
9. There are a lot of little quirky modifiers to track (dodge feat gives the character +1 dodge AC bonus against one target which can be shifted each round, many spell durations are equal to level in rounds, etc.).
10. Incorporeal things are usually tough encounters with only a few specific ways to combat them.