I've purchased Sterlingtek batteries from them direct and from Amazon. I've added three Sterlingtek batteries to three bodies now, so I have two battery changes each for each body and grip.
I had one problem with one of the three I purchased for my 7D2. I contacted Amazon and they credited my card immediately. A few days later, I got an email from Sterlingtek themselves, telling me they were sending me another battery. I emailed them back and let them know Amazon had already taken care of things so I didn't a battery from them. They told me they were sending me a replacement anyway.
I realize we all have different experiences but with my 60D, 70D ... over time.... in both cases, the Sterlingtek batteries kept their performance longer than the Canon batteries. I don't know yet with the 7D2 as I've only had it since November 2014.
What is the voltage of the Sterlingtek.? The Canon LP-e6N has a voltage of 7.2 volts. Some of the 3rd part batteries have a voltage of 7.4 volts or more. A Canon tech advised me today that batteries with a higher than specified 7.2 volts should not be used on the 7DMark II and implied that a higher voltage could potentially cause damage. He also indicated that very often 3rd party batteries don't communicate properly with the camera. I've seen that myself since the extra Watson battery supplied by B&H doesn't communicate remaining power with my 7D II correctly and can go down 20% in a few minutes and then go back up five minutes later.