If you doesn't choose the Sd card right you will have a slow system. however, after that i change for a sd 10 class extreme scan disk that record on 4k videos the performance work fine.
problems that i take when set a slow sd card:
brand tested: scan disk 32gb class 4
brand tested2: multilazer 32gb class10
both brand don't get a good performance.
slow web pages
multi task work with slow
hight I/O write and read.
After change for sd card scan disk 32 gb 4k channel 10 my issue was solved.
follow the tested systems:
android, ok http://www.mediafire.com/file/cabo6z8ky1adgsj/marshrpi3wifibt19042016.img.bz2
raspbian, ok https://www.raspberrypi.org/downloads/
ubuntu core , not yet
windows core, not yet
rtandroid, ok https://rtandroid.embedded.rwth-aachen.de/downloads/raspberry-pi/
kali linux, no yet https://www.offensive-security.com/kali-linux-arm-images/