I use it all the time. Great on foam for sure. Mainly when gluing wing halves togeather on a main spar dihedral brace, nothing better no matter what kind of epoxy you use. If you have a woodpecker it works even better. Works great for mounting horizontal and vertical surfaces to the fuse too. I usually use tape on the joint to force the foaming action back down into the joint. The main caution is to clamp your parts securely because the foam action will jack the pieces apart. Works good for skinning balsa to foam too.

I firmly disagree that it is heavy, definately not any more weight than epoxy over the same area of contact and fill. It's awsome glue.