I just spent a large portion of my day off doing research into 120Hz monitors, and decided to get the BenQ XL2420T. I thought seriously about a "Iiyama ProLite G2773HS", since it is larger and tested to be just as fast, but it doesn't support DisplayPort (very minor, I'm not going to use DisplayPort yet either) and its apparently only really sold in Europe, the US prices for it are very high.
One reason I'm upgrading is that my current monitor's screen is glossy, and I've recently moved and now my computer room receives a lot of light. The reflection are really bad. I need a matte-style screen again, so I used this as an excuse to upgrade.
As for the connector, the one you'll want for 120Hz computer monitors is a "Dual Link DVI" cable, more info here:
http://en.wikipedia.org/wiki/Digital_Visual_Interface#Dual-link_DVI . Which isn't a big deal, the DVI cables I've gotten with my past two monitors were both Dual Link and I didn't even know it, nor did they technically require it. But it is required for 120Hz operation (or DisplayPort), HDMI isn't capable.