+1. Cables definitely matter. Another that is good:

http://www.amazon.com/Fosmon-Vivid-Series-Micro-Cable/dp/B009IZF594/ref=sr_1_2?ie=UTF8&qid=1367759944&sr=8-2&keywords=fosmon+cable

These Fosmon cables come in different colors. For travel, I picked some bright colors as red and green make them easier to spot in a bag and less likely to be left/lost. They are also flat so tangle "resistant". At home, where I have some permanently plugged in to some multi-chargers, color coding tells me which cable is 10A vs 5A. They are designed / rated for 2.1V / 10A.

When I tried to purchase the Kopi ones, they weren't yet available so bought these and have been pretty happy. I may have to get the Kopi cables to do a test.

As an aside, I bought this dock

http://www.amazon.com/RND-Dock-Google-Nexus-Tablet/dp/B008NP7R7S/ref=sr_1_1?ie=UTF8&qid=1367760997&sr=8-1&keywords=rnd+dock+nexus

For my Nexus 7 3g and it charges 2-3 times faster than anything else I have. I need to figure out if it is the charger or cable that came with it.