I am also having the same problem with screen lag, mouse lag and fuzzy.
Lenovo Thinkpad X230T (latest drivers and BIOS)
Windows 8 Pro
Intel HD 4000
Toshiba Dynadock USB 3.0 w/ DisplayLink_7.2M0 drivers and updated firmware connected via DVI-D cable to a BenQ XL2420T monitor using 1920x1080 resolution @ 60hz.
I wish it supported 120hz