Ok, so here are some initial observations on my "Gum Pro" (oh c'mon, who came up with that name...
) device I got recently.
First of all, my Gum Pro wasn't able to provide the declared 1000 mA of current on the USB output. When loaded at 1A with R/C hobby charger in the discharge mode, the "Gum" shut itself down immediately. When I went with the loading current down to 0.5A, it still didn't deliver full 5V but something in the 4.72V range instead. So much for recharging my Hero at full AC adapter rate... Capacity-wise though it performed well, shutting itself down after delivering 2815mAh@4.72V which accounts for a little over 13Wh of usable power so I'm happy with that as it's more or less as much as to be expected from the declared 4400mAh@3.6V battery capacity. Recharging the thingy fully from a powered USB hub took eons (7 hours or so) and I'm yet to see if the things change when using AC USB adapter I got with Hero.
One note regarding recharging: there's a bi-colored LED which is supposed to switch from red to green once the charging is complete. The problem is, that the circuit designers cut some corners and it seems not to actually switch colors but rather start with both green and red lit and then gradually fade the red component down to zero as the charging goes on. So, you have to look at the LED at the "right" angle to be sure it's "just green" already and not "green-red" still
Kinda stupid but not a deal-breaker either.
It has just finished charging my Hero from 4% to 100% in some 2 hours and 15 minutes (2 of the 3 meter LEDs still lit) so while not as fast as using the supplied AC adapter, not really that bad either. So, given the really good price-to-capacity ratio I think I can live with the lower than advertised maximum current and can recommend this product to anyone who doesn't need as-fast-as-possible recharging performance.