Got it today, works the same as a 5w charger. Charges slow when using the machine in a light way, doesn't charge under load and charges about .5% per minute when the lid is closed. It seems to charge about 50% slower than the apple charger.
I like it though because it has extra USB ports to charge my phone and watch. I'm assuming that I won't be able to charge all 3 simultaneously.
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Picked up
http://www.amazon.com/gp/aw/d/B00MOHYJAY today as well. Going to see if I can use that as my travel charger. I don't want to pay $50 for an apple adapter plus $30 for a cable. That seems highly excessive.
I also ordered the Google chromebook pixel charger to see how it fares.
I travel a lot and carry the rMB, iPhone, Apple watch, a USB battery pack, and the requisite cables. I want the most seamless, wire free solution.