Opportunity Fire with Mortars

[J6A]

How often do you find yourself using it.  It's kind of nice that light mortars (well, I guess up to 120mm) have this ability, however it's on the bombardment chart, and unless you have a mortar park (2 or 3 8-10s in adjacent hexes with a leader that can activate them all), the shots aren't that good.  There's no +1 for Op fire, and you would get the +1 for "I can see you", so that's kind of a wash.

I've only used it a couple of times, I'm just curious if others take advantage of it more.