I received a Hero4 Silver over the holidays that I've been tinkering with. Importing video into a computer from the microSD seems sluggish to me, about 40 minutes per 64GB card. I think there is some transcoding going on in the background as I think I read GoPro files are highly compressed. The micro SD card readers or SD adapters may not be that fast to begin with. But my Cannon DSL recorded SD card's video imports much quicker. Copying files over to internal memory may be a faster way to get them into the device. Editing them can be frustrating for us used to near instant gratification
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If all you want to do is create short 5, 15 or 30 second clips, you can do that right on the GoPro Silver's touch display.
If you are recording at the best quality, a battery seems to last an hour or two. Using the 4000 mAh Epic batter add on seems to get maybe 8 hours. You will fill a 64GB SD card in 3 hours. 64GB is the largest card they currently support.
I hear there are competing products with longer lasting batteries that can accommodate larger cards, but I dunno.