I'll believe it when I see a commercial product.

Oh joy! ...one of the only advantages of these noisy flying lawnmowers was that they'd soon leave due to lack of battery. Inevitable I suppose, but still annoying.

"It showed a peak power density of around 560 mW per cubic centimeter at 550° C (1,022° F)"
I'm not sure I want that on my lap or in my pocket.

1/2 watt/ cm**3 ? Not that impressive.

Will they power a piloted quadcopter?

How much & when for fuel cell micro charger, awesome, need for EVs too.

None of these battery claims ever happen. Ever. If you want to put some momentum behind it, make sample packs and send them to ebike groups, remote control websites, e.v forums and let them give some feedback. Why these groups? They are ADDICTED to longer run times and improved efficiency.

First off... kinda click bait when you consider the cell as described would not be able to power a drone for any length of time... let alone hours.
450C-500C? 560mW/CM^3? Hmm...
Lithium ion is 250 to 620 W·h/L. 1L=1000CM^3
So that puts the relative power density of the micro fuel cell, if/when it can be scaled up, to around 560Wh/L. Or around the same as a lithium ion battery.
But... thats _just_ for the fuel cell itself. That does not take into account the volume of the H2 storage system, the control circuits, the batteries to power the control circuit and to initiate the temperature ramp up to 450C-500C.
I'm sure the reaction is exothermic, but a good chunk of power would be consumed maintaining the active/usable temperature range. Which would further reduce the effective energy density of the power supply system as a whole.
You would be looking at a sizable array of at least 14 parallel banks of multiple cells to produce the working voltage and current capacity. That's some serious weight, so you would be looking at a larger drone, which has higher energy requirements.
What this means is that this technology is not meant for civilian drone use, but for military drone use, where the drones are about the size of a small airplane. At that size/scale, it would be practical.
On a DJ Phantom sized drone... lithium remains king, unless you consider using a small ICE engine + generator to convert liquid fuel into electrical power. In which case, that solution would beat the micro fuel cell tech and be more reliable, cost effective, and have parts/tech that is readily available.

I wonder if this will lead to better fuel cells for manned fuel cell vehicles? I think it is a cool and green idea.

Nobody believes in new batteries anymore. The science is there, the tech is there, has been for 20 maybe 30 years in hundreds if not thousands of new iterations and finding, yet new batteries are not there, period.