Finally drained the lumising.
3 recharges of my Samsung Google Nexus (1750 battery) from 15%, being accidentially left on overnight once
1 recharge from red of my 3DS XL (1750) while playing Pokemon X, on the most power intensive settings.
1 recharge of my Nook 1st Edition (1250) from 15%, while reading
I did have some problems with the pack turning itself off while charging my Nook, and the Nook not registering that it's being charged, but that device does have a badly damaged USB port, so I'll let that slide even though I don't have problems with the AC plug as long as I'm careful about the device end of the USB cable.
All in all, I got approxomately 7000 mAh of charge, plus powering the devices' battery usage during the time spent charging. Not bad, when you consider that a good portion of the energy also disappears into the conversion process from the 3.1v lithium battery to the 5v standard USB ports, and then back from the USB standard to the 3.1v lithium batteries inside the devices.
The pack itself takes bloody ages to charge though, and didn't come with it's own charger. But that's to be expected, I suppose. It can only draw 1-1.5a of current while charging, according to the ratings on the brick, so no taking advantage of the full speed of a 2.1a USB wall adapter, if you have one. The short owner's manual that came with it is engrish-y, but understandable, and there are some minor discrepancies in the information stated on the Amazon page, the package, the manual, and the device itself.
For example, it seems to just turn itself off when it has a single flashing light and won't output any charge, but the manual explicitly states that a single flashing light means 10% charge, and that the remaining battery can still be used at that point. Besides that, though, the display from 4 lights to 1 seemed to accurately represent how much power it still had available in comparison to how much I had already used from it. As accurately as it can with only 4 lights, anyway.
An undocumented feature is that the lights will also start staying solid at the same 25% thresholds during charging.
Cosmetically, whatever material the case is made out of attracts fingerprints and skin oils like a high-strength neodymium magnet, and some of the protective plastics are so closely attached they look like they're just part of the case at first, but they mention that in the follow-up email after ordering. All of the edges, including around the on/off button, are a little rough, and the recessed design of said button makes it a bit difficult to press; I have to jab at it with the corner of a fingernail to push it easily; otherwise I'm just kinda pushing on the face of the device while my skin squishes into the shallow hole that the already concave button is in. The pouch is very nice, but it feels like overkill when the device itself is so impossible to keep clean and fancy-looking. Good place to keep all adapters from USB to various other plugs, though.
I suppose that's not bad for just under $27 spent.
Again, thank you all so very much for your assistance in my decision.