I use the glue when making Prairie Points - holds everything in place and, if it's slightly out of line, can easily pull loose and reposition.
I also love gluing down my bindings instead of pinning. That way, I can take the quilt and hand-sew the binding on a long trip and/or while watching TV, without sticking my finger with pins.
If you're trying to piece fabric and match the pattern together glue is the way to go. Just fold over about 1" of the edge of the piece, press it to crease and then, when you match the pattern perfectly, glue it together - flip over and sew along the crease. Perfect matching.