JiaYu G3 indeed looks interesting, I'm wishing for one right when I saw it in the news almost 2 months ago. I used a "Haipai" dual-sim phone for some time, also with the MTK6575 processor and I can say it is ~25% faster than the first implementation of Qualcomm Snapdragon (QSD8250) at 1GHz (I had a HTC HD2). Games I tested were running without much issue - on some newer games I could see a framerate drop, but the game was still playable. I do not play games usually, I mostly hang on the net. Mobile data was faster than even my HTC Sensation. Oh, and I got 2 batteries @2800mAh, with moderate use I got at least 2 full days!
@PaulOBrien: you have to be careful on Aliexpress, order only from shops that have high feedback rates.