Conclusion: D-Link's DIR-857 router, is a decent device and some will be attracted to the built-in SD card reader, but less-than-impressive performance, some issues with rebooting, and some lag streaming high-definition means there are better choices for high-end dual-band routers.
Pros: Up to 450 Mbps on both bands. USB 3.0 port and SD card slot. Easy remote access to connected USB device and SD card. Advanced features. QoS helps with buffering.
Cons: Below average performance Runs hot. Lost Internet connection several times after coming back from reboot.