I don't know what your application is but I switched from using epoxy a while back and started using probond polyeurathane glue after reading an article in High Flight. I works very well at bonding and as it is a foaming glue the only worry is when sheeting with thin balsa sheeting you must make sure you use it sparingly.

It won't completely replace epoxy...

I mix polyurethane glue 50-50 with yellow glue for joining/repairing foam wing core panels, and for filling where chunks were ripped out of a foam wing. Tape the joint or patched area and the foaming action won't rise as much beyond the airfoil shape. (less sanding and shaping) Occasionally there's a huge air bubble that has to be filled again when filling a large void.
The 50-50 mix is also good for some installatins of bylkheads in fiberglass fuselages. Sand the fibreglass a little to ensure the mold release wax orsurfacing wax is gone. (epoxy or poly resin will have a waxy surface, bad for bonding ANY glue.) And... its virtually fuel proof.

Its good stuff... but It shouldn't be used for dihedral braces in built-up wings. The air bubbles mean less bonded area.

Maybe I did not articulate what I was trying to say that well. I still use epoxy for any joints that will require extra strength such as firewalls, landing gear blocks, wing joiners, etc. The polyeurathane is mostly for sheeting foam cores or areas where the foaming action of the glue will compensate for edges that do not exactly fit flush and where this type of glue will benefit the project. For assemby of built up wings I still use CA glue in thin, medium or thick with accelerator. Sometimes if I know that sanding will be required I may opt for the polyeurathane or elmers wood glue as it sands alot easier like when gluing sheets together to make a wing skin. I guess it is whatever preference you as the builder are most satisfied with. I'm sure that by next year there will be something new on the market that is better or stronger, or easier to use.