Tactical squads didn't change at all, except the teleport homers are now half price (a change throughout the entire codex). The only big difference is that they can now take grav-cannons with grav-amps as their heavy weapons. Despite the high cost (a lascannon and missile launcher combined), this is particularly useful for Tactical squads because it is the only heavy weapon effective when moving. It only has a range of 12" on the move but it has 3 AP2 shots, so it will support the squad quite well when deploying from a transport.
Scouts got a massive upgrade. They were raised to WS and BS 4 with no increase in points cost. Beyond that, all the options are the same. This change makes Scouts more effective in both shooting and assault roles, so there's no downside and no special way to take advantage of the change. Scouts are just better.
Crusader squads didn't change much, but their Neophytes do benefit from the increase in Scout WS and BS, so they'll add more to their squad's damage output. Also, it has the benefit that you can roll all of your to hit dice together, so it will speed up your games.