The biggest change is that many missions now have this rule for winning:
WINNING THE GAME
• The Attacker wins if they start their turn with a Tank,
Infantry, or Gun team within 4”/10cm of an Objective,
and end it with no Defending Tank, Infantry, or Gun
teams within 4”/10cm of that Objective.
• The Defender wins if they end a turn on or after the sixth
turn with no Attacking Tank, Infantry, or Gun teams
within 8”/20cm of the Objectives.
This means that the attacker can win if they are close enough to an objective at the start of the turn and then destroy any defending units within 4". This has massive implications for how you defend objectives. No more feeding single teams in just to deny the win to your opponent (which was a particularly favoured tactic of my Soviet tank hordes ).
It also means that the defender doesn't have to basically destroy the attacker to win, as the 16" objective bubble used to effectively mean.