Cover:
If you shooting through more than 2" of cover, then your target gets a cover save.
If there is a dispute about the majority being in or out of cover, thats when the cover save with the -1 comes in.
There is a new category of 4+ cover. This new 4+ cover save applies if you draw LoS through any other unit other than your target.
Normal terrain still has a standardized chart for everything from hedges up to bunkes similar to 4th edition.

Line of Sight:
There are no height levels, all terrain is true LoS (even jungles and woods). They will need to be modeled appropriately if they are to block LoS.

Blast Weapons:
Blast weapons don't roll to hit, but always scatter 2D6" minus the BS of the firer. ~Yikes, watch out for Dark Reaper Exarchs!
All models under a blast template (including partials) are automatically hit. If a "hit" is rolled on the scatter-die it lands on target.

Skimmers:
Skimmers get their cover saves if moving at Cruising speed or All-out.

Missions:
Scoring units must be Troops and Infantry (it is unknown if jump infantry or bikes count towards this).
Killpoints are mostly out, being replaced by the standard VPs in most missions. They remain in a limited fashion in some mission variants. You now score a single killpoint for each unit killed regardless of its FOC category.

Perils of the Warp:
Perils now causes an automatic wound, but invulnerable saves are allowed. They must be rerolled if you pass it the first time, so perils is still dangerous.

Monstrous Creatures:
Monstrous creatures now have the Move Through Cover USR instead of re-rolling the difficult terrain dice.

quelle: belloflostsouls.blogspot.com/

Und immer Volltreffer bei der aktuellen.