OK, this is beginning to bug me. I see a lot of people confusing these two things ALL THE TIME! And worse yet, some people are misinforming others! I'm sick of people telling others to only buy monitors with 1 or 2ms of input lag. While that would be awesome, NO monitor to my knowledge even comes close to those input lag times.
A lot of the confusion is due to both input lag and pixel response times being measured in milliseconds (ms = 1/1000th of a second), and both having to do with display (monitor) performance. However, they're TOTALLY different.
For years, most people only talked about pixel response times. Those are the numbers you see that are less than 5ms. Pixel response time is how long it takes a pixel to change from one color to another. Most manufacturers measure this as GTG (grey-to-grey). Essentially, this is how fast the pixels can change color. The longer the pixel response time is, the more you're likely to see "ghosting" (i.e. after-images or blurring) on your flat panel display during fast moving sequences. Really good monitors range from 1ms to 5ms or so for pixel response GTG times. CRT and Plasma displays, due to the nature of their technology, typically don't have to worry about response times because they're super fast.
Input lag (i.e. Display Lag) is kind of a newer thing that people have been measuring (and a lot of people don't quite understand.) Input lag is how long it takes for a display to show an input on your screen. For example, input lag measures how long it takes from when you press the light punch button to when the action is displayed. To my knowledge no display manufacturer publishes this value. Maybe they will soon because it's becoming a hot topic... especially in the fighting game community, but I've yet to see places like amazon.com or newegg.com list input lag values for a display. So if you see a low ms value listed on a website where you're buying something, you're most likely seeing the pixel response time, not this. A really good input lag rating is about 10ms. Anywhere from 10ms to 40ms is considered pretty good. Above 40ms, and you'll start to notice a delay from when you punch to when you see it. AFAIK, THERE ARE NO COMMERICALLY AVAILABLE 1ms INPUT LAG MONITORS. Not by Asus or Benq or anyone else.
For a database of input lag (i.e. display lag) ratings, check http://www.displaylag.com/display-database/
To be perfectly honest, how well a display performs for gaming is going to be due to a combination of both input lag and pixel response times. Both are important. And high values for either can cause your game controls to feel sluggish.
Bonus: While I'm at it... Refresh Rates are something completely different too. But, most people don't confuse them with input lag or pixel respone times because they're measured in Hz as opposed to ms. A 60Hz monitor is standard and refreshes 60 times a second. Higher performance monitors can do 120Hz (120 times a second) and some gamer specific models are rated as 144Hz. You'll even see some displays listed as 240Hz or 480Hz. Plasma displays don't work like LCDs do, but to complete with the Hz-heavy marketing used by LCD manufacturers, they typically list plasmas as 600Hz. Unless you're doing 3D (which requires 120HZ or more), you don't need to worry about this too much. For fighting games, 60Hz is fine as most games run at 60 frames per second anyway.