I haven't got my G3 yet (still in the mail) but I'm looking into getting a battery like this because:
My note 2 doesn't want to get a signal anymore so while i wait for my g3, I'm using a mates old galaxy s3; the usb port is busted so he bought a wall charger and a "gold" 3250 mAh, as well as keeping his stock 2100 mAh one.
The gold one doesnt use a special back cover, it fits in the standard one, but it is slightly bigger. It bulges like a belly at a buffet.
It lasts me from 8am to about 11pm and thats with moderate use, browsing and facebook most of the day (during work lol)
the stock battery barely makes it till morning from when i switch them out, so back in goes goldmember.
The cheap one also seems to get less hot than the stock one for some reason.
>This is the G3's version of my current battery<
So yeah, that's my two cents.
Maybe its luck of the draw?