For players who frequently switch between playing Descent and Imperial Assault, what are the most commonly forgotten rule differences?

For Example:

Descent: Hostile figures block movement unless an ability supersedes it

IA: Hostile figures are treated as Difficult Terrain (1 extra MP per space moved through)

One that often gets me is that only 2 strain can be used per turn to gain movement points in IA, while you can use as many as you have available in Descent.

The line of sight rules are different too, but I use IA’s LoS rules in my Descent games so I don’t have to worry about that.

Another gotcha is that you can move diagonally through a corner that has blocking terrain lines meeting at that corner in Descent. In fact, you have to in certain maps, such as the final tile of the Intro map in Mists of Bilehall. In IA, you cannot move through these corners, nor draw line of sight through them.

I will add : special actions (with action icon)
Descent : the same special action can be triggered many times, limited only by the number of available actions
IA: a special action can only used once per activation