Just wanted to let you guys know that I've been messing with these today. The documents that Cyan gave us regarding how these work is wrong.
They say: "It specifies an object's Z-axis as always facing the viewer and....."
In Blender with the GoW Plugin, we always had to make sure that the Z axis was facing AWAY from the viewer. I wasn't concerned about this at first, as there are some things that are different between the Cyan Plugin and the GoW Plugin.
However when I tested this today, leaving the local Z axis of my plane facing towards where the avatar would see, you could not see the light glare.
I went back into Max, and while in Local, rotated the pivot point Z axis of my plane AWAY from where the avatar would see, and on export, the light glare worked just fine.
So I'm afraid their document is wrong or out of date. It should read: "It specifies an object's Z-axis as always facing away from the viewer and....."
Emphasis mine. Oh, and it's pretty cool the way you can use the Billboard so it pivots on the Y axis only, or use Sprite for it to pivot on any axis.