Top of my list of things that I picked up this week:
If playing with a monstrous creature that can deep strike (I'm looking at you greater daemons of Tzeentch and Khorne), they can come in to play in the "swooping" mode.
When doing so, we can elect to deepstrike them in to ruins (they'll hit the ground level) or other buildings. Since monstrous creatures all get the move through cover universal special rule, they do not need to take any dangerous terrain tests.
More significantly, enemies need 6+ to hit them, and they benefit from a 4+ cover save. Nice.
Citation: Imperius Dominatus and others locally (i.e. from real world conversations!) covered this earlier this week.