The restrictions on normal direct fire are gone, allowing you to attack any combination of defenders in the stack. No area fire, a spotter is still required to have spotted a target unit or be adjacent. Line of Sight is straight edge. Spotting includes being able to spot units which fire. You no longer need to be adjacent to see such units, and trucks and wagons may no longer spot.
Engineers now add a lot of chrome, with demolitions and clearing minefields and blocks.
The allies also get some neat engineering vehicles to clear mines, lay bridges, and use flame throwers. Figher bombers can terrorize German tanks, though the Germans get some AA to shoot back. Optional rules include Infantry quick march, Opportunity Fire, Naval Support Fire, and Panzerblitz assualt. In PB, if you have enough artillery around, you can wipe out any defensive position a piece at a time, assuming you can keep your spotters alive.