I know that many who see those 100 - 120 MB/s reported speeds think that they seem slow..
Remember most apps report MegaBYTE(s) per second, and in today's connected world we are used to seeing transfer rates of 50, 70, and 115 Mbps - Mega
bits per second..
So that 100 MB/s translates to about 839 Mbps and your 120 MB/sec comes to about 1 Gbps. In no way should that be considered "slow".
_in theory_ a file transfer at the usb 3.0 "max" speed of 5 Gbps would roughly be reported at about 590 MB/s by windows explorer..
Now for me.. the real world file transfers I am seeing when sending files from my windows desktop via 1 Gbps ethernet, down to an external 2 TB Seagate Expansion Disk connected via USB 3.0 to my Asus RT-N65U router are in the neighborhood of about 114-123 Mbps..
Which is decent compared to the previous drive, a 1.5 TB Western Digital "Green" drive connected to the same router with USB 2.0 .. On a good day I would see 20-24 Mbps.. Have large files to move? start transfer, go shopping, come back in a few hours, see transfers still chugging along.. Go read a book or two while waiting for transfers to complete.