I have three of these, if that tells you anything.
I love being able to swap different fuel in and out of my totebox.
Yes, it can be frustrating at time trying to thread this cap onto gallon jugs, but the problem is not the cap - it's the plastic bottles. The cap is CNC machined to great precision compared to the cheap plastic bottles, which can vary in quality from manufacturer to manufacturer, or even batch to batch.
I have crossed threads on a few jugs, but I haven't yet found a jug that I couldn't manage to thread onto properly if I take my time with it.
Don't know if this is worth anything, but don't give up on it. I've tried many different ways of capping a fuel bottle with fuel fittings, and this is by far the best way. Seals great (once you get it to seat right) and the rubber o-ring is replaceable, which means this cap will last practically forever.