I bought the Dell Inspiron 7548 on the February this year (2015) and i never got my usb 3.0 port working correctly.
Basically what happens is that every time I plug a usb 3 stick or an external hdd (in this case a 2.5 hdd) i get the micosoft pluged in device sound and immediately a unplug sound. This is something intermittently until I completely unplug the device. Needless is to say that the device does not shows up with stability on the computer. (Basically the safe device reject on the lower right corner of the windows bar also shows up and disappears guided by the plug and unplug sound).
I think I tried everything. From having my laptop with all the power options settings to High performance...from disabling power saving on each USB device at device manager...as well as disabling powershare and emulation at bios...as well as enabling debug mode which makes the USB 3 port turns to a USB 2 port..obviously this is not what I want.
Also. USB 2 port (the only one on this laptop) Works just fine with anything I plug.