[Ikarus]

Shooting
-There's now a reason to have a BS higher than 5 (can we say 2+/5+?).
-All models friend or foe now block line of sight. Vehicles and Monstrous Creature can be targeted over intervening infantry.
-Area terrain does not block line of sight.
-All blast weapons now scatter. BS is still an important function of how far though.

Vehicles
-Defensive weapons on vehicles are now Str 4 and below.
--Skimmers Moving Fast is now a 5+ cover save. All Obscured Targets receive a cover save. No more "Hull Down."
-Dedicated transports can now carry any unit (subject to normal restrictions, i.e., no Terminators) and are no longer the deathtraps they have been (no entangling, just pinning).
-AP 1 weapons add +1 to the vehicle damage chart instead of doing as they do now.
-Ordinance weapons roll 2d6 and pick the highest on the vehicle damage table.

Miscellaneous
-Independent Character targeting restrictions have been eased.
-There is no IC protection any longer unless he is joined to a unit
-ICs within 2" of a unit automatically join it.
-Dark Eldar are not gone, as they're mentioned in the rules (their jetbikes DO get the 6" assault).
-Frag grenades operate as plasma grenades now.
-Monstrous creatures get move through cover, not a reroll.
-Saving Throws are now made AFTER wound allocation. This means you could still roll all your generic troopers as a group, but will need to roll for each special model (serg, heavy weapons, etc) one by one. Torrent of Fire is gone.

Missions
-The missions are different enough that Troops only counting as scoring isn't as big a deal as it would be today.
-Victory points are calculated differently in "cleanse" style missions (points calculated depending on the FOC slot the dead unit took up).
-Scouts and Infiltrators can now try to outflank the enemy and come on as reserves from a different board edge.
-Deepstrike is the same, but if you can't place all the models, you roll on the "deepstrike mishap" table (50% you're dead, 50% you place yourself anywhere you like).