I have owned the Powercore Fusion now for 6 weeks and I've traveled a total of 4 trips and 16000 miles and the Fusion hasn't got used ever.
Possibly the situation might arise but seems when I'm packing it just doesn't ever fit the needs.
Take in point a long day return I got to LAX coming on Friday, the nature of what I'm doing that day only really needs my mobile and say a small tablet, chances are probably the battery life of those 2 devices is enough and so probably I could get away with nothing Anker. But then just in case, such as if my return flight is delayed seriously and I'm using my phone to watch videos to kill time, and if delayed flight caused the terminal to be busy I might find a mains socket hard to find. Perfect example of needing something small just in case. So I could just carry say the Powercore Slim 5000 (v small) but a Powercore 10000 would be more useful. The Powercore Fusion is BIGGER than the Powercore 10000. If I go the other way of carrying the phone charger and say the Powercore 5000 then I got a few more corner situations covered, or say the Powerport2 and the Powercore 5000 even more corners covered.
If it were that size and say 10000mah or that size and it was say 6A of output, then it begins to become useful.
It the fact the Fusion is so big and it isn't either a large battery capacity like the 10000 nor is it a fast charger or two fast charging ports, means its basically not very good at anything, so when I throw my stuff in my pockets, the Fusion is left at home.
Just back from 2 weeks across 3 countries and I was with Powerport2 and Powercore 1000, and a very long mains cable to which I added either a UK or EU adapter.